diff --git a/core/fpdfapi/render/BUILD.gn b/core/fpdfapi/render/BUILD.gn
index 8378de6..d7cc9b6 100644
--- a/core/fpdfapi/render/BUILD.gn
+++ b/core/fpdfapi/render/BUILD.gn
@@ -30,6 +30,8 @@
     "cpdf_rendercontext.h",
     "cpdf_renderoptions.cpp",
     "cpdf_renderoptions.h",
+    "cpdf_rendershading.cpp",
+    "cpdf_rendershading.h",
     "cpdf_renderstatus.cpp",
     "cpdf_renderstatus.h",
     "cpdf_scaledrenderbuffer.cpp",
diff --git a/core/fpdfapi/render/cpdf_rendershading.cpp b/core/fpdfapi/render/cpdf_rendershading.cpp
new file mode 100644
index 0000000..0ac8043
--- /dev/null
+++ b/core/fpdfapi/render/cpdf_rendershading.cpp
@@ -0,0 +1,954 @@
+// Copyright 2019 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#include "core/fpdfapi/render/cpdf_rendershading.h"
+
+#include <algorithm>
+#include <array>
+#include <cmath>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "core/fpdfapi/page/cpdf_colorspace.h"
+#include "core/fpdfapi/page/cpdf_dibbase.h"
+#include "core/fpdfapi/page/cpdf_function.h"
+#include "core/fpdfapi/page/cpdf_meshstream.h"
+#include "core/fpdfapi/parser/cpdf_array.h"
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+#include "core/fpdfapi/parser/cpdf_stream.h"
+#include "core/fpdfapi/parser/fpdf_parser_utility.h"
+#include "core/fpdfapi/render/cpdf_devicebuffer.h"
+#include "core/fpdfapi/render/cpdf_renderoptions.h"
+#include "core/fxcrt/fx_safe_types.h"
+#include "core/fxcrt/fx_system.h"
+#include "core/fxge/cfx_defaultrenderdevice.h"
+#include "core/fxge/dib/cfx_dibitmap.h"
+#include "core/fxge/fx_dib.h"
+
+namespace {
+
+constexpr int kShadingSteps = 256;
+
+uint32_t CountOutputsFromFunctions(
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs) {
+  FX_SAFE_UINT32 total = 0;
+  for (const auto& func : funcs) {
+    if (func)
+      total += func->CountOutputs();
+  }
+  return total.ValueOrDefault(0);
+}
+
+uint32_t GetValidatedOutputsCount(
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+    const RetainPtr<CPDF_ColorSpace>& pCS) {
+  uint32_t funcs_outputs = CountOutputsFromFunctions(funcs);
+  return funcs_outputs ? std::max(funcs_outputs, pCS->CountComponents()) : 0;
+}
+
+std::array<FX_ARGB, kShadingSteps> GetShadingSteps(
+    float t_min,
+    float t_max,
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+    const RetainPtr<CPDF_ColorSpace>& pCS,
+    int alpha,
+    size_t results_count) {
+  ASSERT(results_count >= CountOutputsFromFunctions(funcs));
+  ASSERT(results_count >= pCS->CountComponents());
+  std::array<FX_ARGB, kShadingSteps> shading_steps;
+  std::vector<float> result_array(results_count);
+  float diff = t_max - t_min;
+  for (int i = 0; i < kShadingSteps; ++i) {
+    float input = diff * i / kShadingSteps + t_min;
+    int offset = 0;
+    for (const auto& func : funcs) {
+      if (func) {
+        int nresults = 0;
+        if (func->Call(&input, 1, &result_array[offset], &nresults))
+          offset += nresults;
+      }
+    }
+    float R = 0.0f;
+    float G = 0.0f;
+    float B = 0.0f;
+    pCS->GetRGB(result_array.data(), &R, &G, &B);
+    shading_steps[i] =
+        FXARGB_TODIB(ArgbEncode(alpha, FXSYS_roundf(R * 255),
+                                FXSYS_roundf(G * 255), FXSYS_roundf(B * 255)));
+  }
+  return shading_steps;
+}
+
+void DrawAxialShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
+                      const CFX_Matrix& mtObject2Bitmap,
+                      const CPDF_Dictionary* pDict,
+                      const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+                      const RetainPtr<CPDF_ColorSpace>& pCS,
+                      int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+
+  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
+  if (total_results == 0)
+    return;
+
+  const CPDF_Array* pCoords = pDict->GetArrayFor("Coords");
+  if (!pCoords)
+    return;
+
+  float start_x = pCoords->GetNumberAt(0);
+  float start_y = pCoords->GetNumberAt(1);
+  float end_x = pCoords->GetNumberAt(2);
+  float end_y = pCoords->GetNumberAt(3);
+  float t_min = 0;
+  float t_max = 1.0f;
+  const CPDF_Array* pArray = pDict->GetArrayFor("Domain");
+  if (pArray) {
+    t_min = pArray->GetNumberAt(0);
+    t_max = pArray->GetNumberAt(1);
+  }
+  pArray = pDict->GetArrayFor("Extend");
+  const bool bStartExtend = pArray && pArray->GetBooleanAt(0, false);
+  const bool bEndExtend = pArray && pArray->GetBooleanAt(1, false);
+
+  int width = pBitmap->GetWidth();
+  int height = pBitmap->GetHeight();
+  float x_span = end_x - start_x;
+  float y_span = end_y - start_y;
+  float axis_len_square = (x_span * x_span) + (y_span * y_span);
+
+  std::array<FX_ARGB, kShadingSteps> shading_steps =
+      GetShadingSteps(t_min, t_max, funcs, pCS, alpha, total_results);
+
+  int pitch = pBitmap->GetPitch();
+  CFX_Matrix matrix = mtObject2Bitmap.GetInverse();
+  for (int row = 0; row < height; row++) {
+    uint32_t* dib_buf =
+        reinterpret_cast<uint32_t*>(pBitmap->GetBuffer() + row * pitch);
+    for (int column = 0; column < width; column++) {
+      CFX_PointF pos = matrix.Transform(
+          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
+      float scale =
+          (((pos.x - start_x) * x_span) + ((pos.y - start_y) * y_span)) /
+          axis_len_square;
+      int index = (int32_t)(scale * (kShadingSteps - 1));
+      if (index < 0) {
+        if (!bStartExtend)
+          continue;
+
+        index = 0;
+      } else if (index >= kShadingSteps) {
+        if (!bEndExtend)
+          continue;
+
+        index = kShadingSteps - 1;
+      }
+      dib_buf[column] = shading_steps[index];
+    }
+  }
+}
+
+void DrawRadialShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
+                       const CFX_Matrix& mtObject2Bitmap,
+                       const CPDF_Dictionary* pDict,
+                       const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+                       const RetainPtr<CPDF_ColorSpace>& pCS,
+                       int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+
+  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
+  if (total_results == 0)
+    return;
+
+  const CPDF_Array* pCoords = pDict->GetArrayFor("Coords");
+  if (!pCoords)
+    return;
+
+  float start_x = pCoords->GetNumberAt(0);
+  float start_y = pCoords->GetNumberAt(1);
+  float start_r = pCoords->GetNumberAt(2);
+  float end_x = pCoords->GetNumberAt(3);
+  float end_y = pCoords->GetNumberAt(4);
+  float end_r = pCoords->GetNumberAt(5);
+  float t_min = 0;
+  float t_max = 1.0f;
+  const CPDF_Array* pArray = pDict->GetArrayFor("Domain");
+  if (pArray) {
+    t_min = pArray->GetNumberAt(0);
+    t_max = pArray->GetNumberAt(1);
+  }
+  pArray = pDict->GetArrayFor("Extend");
+  const bool bStartExtend = pArray && pArray->GetBooleanAt(0, false);
+  const bool bEndExtend = pArray && pArray->GetBooleanAt(1, false);
+
+  std::array<FX_ARGB, kShadingSteps> shading_steps =
+      GetShadingSteps(t_min, t_max, funcs, pCS, alpha, total_results);
+
+  const float dx = end_x - start_x;
+  const float dy = end_y - start_y;
+  const float dr = end_r - start_r;
+  const float a = dx * dx + dy * dy - dr * dr;
+  const bool a_is_float_zero = IsFloatZero(a);
+
+  int width = pBitmap->GetWidth();
+  int height = pBitmap->GetHeight();
+  int pitch = pBitmap->GetPitch();
+
+  bool bDecreasing =
+      (dr < 0 && static_cast<int>(sqrt(dx * dx + dy * dy)) < -dr);
+
+  CFX_Matrix matrix = mtObject2Bitmap.GetInverse();
+  for (int row = 0; row < height; row++) {
+    uint32_t* dib_buf =
+        reinterpret_cast<uint32_t*>(pBitmap->GetBuffer() + row * pitch);
+    for (int column = 0; column < width; column++) {
+      CFX_PointF pos = matrix.Transform(
+          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
+      float pos_dx = pos.x - start_x;
+      float pos_dy = pos.y - start_y;
+      float b = -2 * (pos_dx * dx + pos_dy * dy + start_r * dr);
+      float c = pos_dx * pos_dx + pos_dy * pos_dy - start_r * start_r;
+      float s;
+      if (IsFloatZero(b)) {
+        s = sqrt(-c / a);
+      } else if (a_is_float_zero) {
+        s = -c / b;
+      } else {
+        float b2_4ac = (b * b) - 4 * (a * c);
+        if (b2_4ac < 0)
+          continue;
+
+        float root = sqrt(b2_4ac);
+        float s1 = (-b - root) / (2 * a);
+        float s2 = (-b + root) / (2 * a);
+        if (a <= 0)
+          std::swap(s1, s2);
+        if (bDecreasing)
+          s = (s1 >= 0 || bStartExtend) ? s1 : s2;
+        else
+          s = (s2 <= 1.0f || bEndExtend) ? s2 : s1;
+
+        if (start_r + s * dr < 0)
+          continue;
+      }
+
+      int index = static_cast<int32_t>(s * (kShadingSteps - 1));
+      if (index < 0) {
+        if (!bStartExtend)
+          continue;
+        index = 0;
+      } else if (index >= kShadingSteps) {
+        if (!bEndExtend)
+          continue;
+        index = kShadingSteps - 1;
+      }
+      dib_buf[column] = shading_steps[index];
+    }
+  }
+}
+
+void DrawFuncShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
+                     const CFX_Matrix& mtObject2Bitmap,
+                     const CPDF_Dictionary* pDict,
+                     const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+                     const RetainPtr<CPDF_ColorSpace>& pCS,
+                     int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+
+  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
+  if (total_results == 0)
+    return;
+
+  const CPDF_Array* pDomain = pDict->GetArrayFor("Domain");
+  float xmin = 0.0f;
+  float ymin = 0.0f;
+  float xmax = 1.0f;
+  float ymax = 1.0f;
+  if (pDomain) {
+    xmin = pDomain->GetNumberAt(0);
+    xmax = pDomain->GetNumberAt(1);
+    ymin = pDomain->GetNumberAt(2);
+    ymax = pDomain->GetNumberAt(3);
+  }
+  CFX_Matrix mtDomain2Target = pDict->GetMatrixFor("Matrix");
+  CFX_Matrix matrix =
+      mtObject2Bitmap.GetInverse() * mtDomain2Target.GetInverse();
+  int width = pBitmap->GetWidth();
+  int height = pBitmap->GetHeight();
+  int pitch = pBitmap->GetPitch();
+
+  ASSERT(total_results >= CountOutputsFromFunctions(funcs));
+  ASSERT(total_results >= pCS->CountComponents());
+  std::vector<float> result_array(total_results);
+  for (int row = 0; row < height; ++row) {
+    uint32_t* dib_buf = (uint32_t*)(pBitmap->GetBuffer() + row * pitch);
+    for (int column = 0; column < width; column++) {
+      CFX_PointF pos = matrix.Transform(
+          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
+      if (pos.x < xmin || pos.x > xmax || pos.y < ymin || pos.y > ymax)
+        continue;
+
+      float input[] = {pos.x, pos.y};
+      int offset = 0;
+      for (const auto& func : funcs) {
+        if (func) {
+          int nresults;
+          if (func->Call(input, 2, &result_array[offset], &nresults))
+            offset += nresults;
+        }
+      }
+
+      float R = 0.0f;
+      float G = 0.0f;
+      float B = 0.0f;
+      pCS->GetRGB(result_array.data(), &R, &G, &B);
+      dib_buf[column] = FXARGB_TODIB(ArgbEncode(
+          alpha, (int32_t)(R * 255), (int32_t)(G * 255), (int32_t)(B * 255)));
+    }
+  }
+}
+
+bool GetScanlineIntersect(int y,
+                          const CFX_PointF& first,
+                          const CFX_PointF& second,
+                          float* x) {
+  if (first.y == second.y)
+    return false;
+
+  if (first.y < second.y) {
+    if (y < first.y || y > second.y)
+      return false;
+  } else if (y < second.y || y > first.y) {
+    return false;
+  }
+  *x = first.x + ((second.x - first.x) * (y - first.y) / (second.y - first.y));
+  return true;
+}
+
+void DrawGouraud(const RetainPtr<CFX_DIBitmap>& pBitmap,
+                 int alpha,
+                 CPDF_MeshVertex triangle[3]) {
+  float min_y = triangle[0].position.y;
+  float max_y = triangle[0].position.y;
+  for (int i = 1; i < 3; i++) {
+    min_y = std::min(min_y, triangle[i].position.y);
+    max_y = std::max(max_y, triangle[i].position.y);
+  }
+  if (min_y == max_y)
+    return;
+
+  int min_yi = std::max(static_cast<int>(floor(min_y)), 0);
+  int max_yi = static_cast<int>(ceil(max_y));
+
+  if (max_yi >= pBitmap->GetHeight())
+    max_yi = pBitmap->GetHeight() - 1;
+
+  for (int y = min_yi; y <= max_yi; y++) {
+    int nIntersects = 0;
+    float inter_x[3];
+    float r[3];
+    float g[3];
+    float b[3];
+    for (int i = 0; i < 3; i++) {
+      CPDF_MeshVertex& vertex1 = triangle[i];
+      CPDF_MeshVertex& vertex2 = triangle[(i + 1) % 3];
+      CFX_PointF& position1 = vertex1.position;
+      CFX_PointF& position2 = vertex2.position;
+      bool bIntersect =
+          GetScanlineIntersect(y, position1, position2, &inter_x[nIntersects]);
+      if (!bIntersect)
+        continue;
+
+      float y_dist = (y - position1.y) / (position2.y - position1.y);
+      r[nIntersects] = vertex1.r + ((vertex2.r - vertex1.r) * y_dist);
+      g[nIntersects] = vertex1.g + ((vertex2.g - vertex1.g) * y_dist);
+      b[nIntersects] = vertex1.b + ((vertex2.b - vertex1.b) * y_dist);
+      nIntersects++;
+    }
+    if (nIntersects != 2)
+      continue;
+
+    int min_x, max_x, start_index, end_index;
+    if (inter_x[0] < inter_x[1]) {
+      min_x = (int)floor(inter_x[0]);
+      max_x = (int)ceil(inter_x[1]);
+      start_index = 0;
+      end_index = 1;
+    } else {
+      min_x = (int)floor(inter_x[1]);
+      max_x = (int)ceil(inter_x[0]);
+      start_index = 1;
+      end_index = 0;
+    }
+
+    int start_x = std::max(min_x, 0);
+    int end_x = max_x;
+    if (end_x > pBitmap->GetWidth())
+      end_x = pBitmap->GetWidth();
+
+    uint8_t* dib_buf =
+        pBitmap->GetBuffer() + y * pBitmap->GetPitch() + start_x * 4;
+    float r_unit = (r[end_index] - r[start_index]) / (max_x - min_x);
+    float g_unit = (g[end_index] - g[start_index]) / (max_x - min_x);
+    float b_unit = (b[end_index] - b[start_index]) / (max_x - min_x);
+    float R = r[start_index] + (start_x - min_x) * r_unit;
+    float G = g[start_index] + (start_x - min_x) * g_unit;
+    float B = b[start_index] + (start_x - min_x) * b_unit;
+    for (int x = start_x; x < end_x; x++) {
+      R += r_unit;
+      G += g_unit;
+      B += b_unit;
+      FXARGB_SETDIB(dib_buf,
+                    ArgbEncode(alpha, (int32_t)(R * 255), (int32_t)(G * 255),
+                               (int32_t)(B * 255)));
+      dib_buf += 4;
+    }
+  }
+}
+
+void DrawFreeGouraudShading(
+    const RetainPtr<CFX_DIBitmap>& pBitmap,
+    const CFX_Matrix& mtObject2Bitmap,
+    const CPDF_Stream* pShadingStream,
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+    const RetainPtr<CPDF_ColorSpace>& pCS,
+    int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+
+  CPDF_MeshStream stream(kFreeFormGouraudTriangleMeshShading, funcs,
+                         pShadingStream, pCS);
+  if (!stream.Load())
+    return;
+
+  CPDF_MeshVertex triangle[3];
+  memset(triangle, 0, sizeof(triangle));
+
+  while (!stream.BitStream()->IsEOF()) {
+    CPDF_MeshVertex vertex;
+    uint32_t flag;
+    if (!stream.ReadVertex(mtObject2Bitmap, &vertex, &flag))
+      return;
+
+    if (flag == 0) {
+      triangle[0] = vertex;
+      for (int j = 1; j < 3; j++) {
+        uint32_t tflag;
+        if (!stream.ReadVertex(mtObject2Bitmap, &triangle[j], &tflag))
+          return;
+      }
+    } else {
+      if (flag == 1)
+        triangle[0] = triangle[1];
+
+      triangle[1] = triangle[2];
+      triangle[2] = vertex;
+    }
+    DrawGouraud(pBitmap, alpha, triangle);
+  }
+}
+
+void DrawLatticeGouraudShading(
+    const RetainPtr<CFX_DIBitmap>& pBitmap,
+    const CFX_Matrix& mtObject2Bitmap,
+    const CPDF_Stream* pShadingStream,
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+    const RetainPtr<CPDF_ColorSpace>& pCS,
+    int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+
+  int row_verts = pShadingStream->GetDict()->GetIntegerFor("VerticesPerRow");
+  if (row_verts < 2)
+    return;
+
+  CPDF_MeshStream stream(kLatticeFormGouraudTriangleMeshShading, funcs,
+                         pShadingStream, pCS);
+  if (!stream.Load())
+    return;
+
+  std::vector<CPDF_MeshVertex> vertices[2];
+  vertices[0] = stream.ReadVertexRow(mtObject2Bitmap, row_verts);
+  if (vertices[0].empty())
+    return;
+
+  int last_index = 0;
+  while (1) {
+    vertices[1 - last_index] = stream.ReadVertexRow(mtObject2Bitmap, row_verts);
+    if (vertices[1 - last_index].empty())
+      return;
+
+    CPDF_MeshVertex triangle[3];
+    for (int i = 1; i < row_verts; ++i) {
+      triangle[0] = vertices[last_index][i];
+      triangle[1] = vertices[1 - last_index][i - 1];
+      triangle[2] = vertices[last_index][i - 1];
+      DrawGouraud(pBitmap, alpha, triangle);
+      triangle[2] = vertices[1 - last_index][i];
+      DrawGouraud(pBitmap, alpha, triangle);
+    }
+    last_index = 1 - last_index;
+  }
+}
+
+struct Coon_BezierCoeff {
+  float a, b, c, d;
+  void FromPoints(float p0, float p1, float p2, float p3) {
+    a = -p0 + 3 * p1 - 3 * p2 + p3;
+    b = 3 * p0 - 6 * p1 + 3 * p2;
+    c = -3 * p0 + 3 * p1;
+    d = p0;
+  }
+  Coon_BezierCoeff first_half() {
+    Coon_BezierCoeff result;
+    result.a = a / 8;
+    result.b = b / 4;
+    result.c = c / 2;
+    result.d = d;
+    return result;
+  }
+  Coon_BezierCoeff second_half() {
+    Coon_BezierCoeff result;
+    result.a = a / 8;
+    result.b = 3 * a / 8 + b / 4;
+    result.c = 3 * a / 8 + b / 2 + c / 2;
+    result.d = a / 8 + b / 4 + c / 2 + d;
+    return result;
+  }
+  void GetPoints(float p[4]) {
+    p[0] = d;
+    p[1] = c / 3 + p[0];
+    p[2] = b / 3 - p[0] + 2 * p[1];
+    p[3] = a + p[0] - 3 * p[1] + 3 * p[2];
+  }
+  void GetPointsReverse(float p[4]) {
+    p[3] = d;
+    p[2] = c / 3 + p[3];
+    p[1] = b / 3 - p[3] + 2 * p[2];
+    p[0] = a + p[3] - 3 * p[2] + 3 * p[1];
+  }
+  void BezierInterpol(Coon_BezierCoeff& C1,
+                      Coon_BezierCoeff& C2,
+                      Coon_BezierCoeff& D1,
+                      Coon_BezierCoeff& D2) {
+    a = (D1.a + D2.a) / 2;
+    b = (D1.b + D2.b) / 2;
+    c = (D1.c + D2.c) / 2 - (C1.a / 8 + C1.b / 4 + C1.c / 2) +
+        (C2.a / 8 + C2.b / 4) + (-C1.d + D2.d) / 2 - (C2.a + C2.b) / 2;
+    d = C1.a / 8 + C1.b / 4 + C1.c / 2 + C1.d;
+  }
+  float Distance() {
+    float dis = a + b + c;
+    return dis < 0 ? -dis : dis;
+  }
+};
+
+struct Coon_Bezier {
+  Coon_BezierCoeff x, y;
+  void FromPoints(float x0,
+                  float y0,
+                  float x1,
+                  float y1,
+                  float x2,
+                  float y2,
+                  float x3,
+                  float y3) {
+    x.FromPoints(x0, x1, x2, x3);
+    y.FromPoints(y0, y1, y2, y3);
+  }
+
+  Coon_Bezier first_half() {
+    Coon_Bezier result;
+    result.x = x.first_half();
+    result.y = y.first_half();
+    return result;
+  }
+
+  Coon_Bezier second_half() {
+    Coon_Bezier result;
+    result.x = x.second_half();
+    result.y = y.second_half();
+    return result;
+  }
+
+  void BezierInterpol(Coon_Bezier& C1,
+                      Coon_Bezier& C2,
+                      Coon_Bezier& D1,
+                      Coon_Bezier& D2) {
+    x.BezierInterpol(C1.x, C2.x, D1.x, D2.x);
+    y.BezierInterpol(C1.y, C2.y, D1.y, D2.y);
+  }
+
+  void GetPoints(std::vector<FX_PATHPOINT>& pPoints, size_t start_idx) {
+    float p[4];
+    int i;
+    x.GetPoints(p);
+    for (i = 0; i < 4; i++)
+      pPoints[start_idx + i].m_Point.x = p[i];
+
+    y.GetPoints(p);
+    for (i = 0; i < 4; i++)
+      pPoints[start_idx + i].m_Point.y = p[i];
+  }
+
+  void GetPointsReverse(std::vector<FX_PATHPOINT>& pPoints, size_t start_idx) {
+    float p[4];
+    int i;
+    x.GetPointsReverse(p);
+    for (i = 0; i < 4; i++)
+      pPoints[i + start_idx].m_Point.x = p[i];
+
+    y.GetPointsReverse(p);
+    for (i = 0; i < 4; i++)
+      pPoints[i + start_idx].m_Point.y = p[i];
+  }
+
+  float Distance() { return x.Distance() + y.Distance(); }
+};
+
+int Interpolate(int p1, int p2, int delta1, int delta2, bool* overflow) {
+  pdfium::base::CheckedNumeric<int> p = p2;
+  p -= p1;
+  p *= delta1;
+  p /= delta2;
+  p += p1;
+  if (!p.IsValid())
+    *overflow = true;
+  return p.ValueOrDefault(0);
+}
+
+int BiInterpolImpl(int c0,
+                   int c1,
+                   int c2,
+                   int c3,
+                   int x,
+                   int y,
+                   int x_scale,
+                   int y_scale,
+                   bool* overflow) {
+  int x1 = Interpolate(c0, c3, x, x_scale, overflow);
+  int x2 = Interpolate(c1, c2, x, x_scale, overflow);
+  return Interpolate(x1, x2, y, y_scale, overflow);
+}
+
+struct Coon_Color {
+  Coon_Color() { memset(comp, 0, sizeof(int) * 3); }
+
+  // Returns true if successful, false if overflow detected.
+  bool BiInterpol(Coon_Color colors[4],
+                  int x,
+                  int y,
+                  int x_scale,
+                  int y_scale) {
+    bool overflow = false;
+    for (int i = 0; i < 3; i++) {
+      comp[i] = BiInterpolImpl(colors[0].comp[i], colors[1].comp[i],
+                               colors[2].comp[i], colors[3].comp[i], x, y,
+                               x_scale, y_scale, &overflow);
+    }
+    return !overflow;
+  }
+
+  int Distance(Coon_Color& o) {
+    return std::max({abs(comp[0] - o.comp[0]), abs(comp[1] - o.comp[1]),
+                     abs(comp[2] - o.comp[2])});
+  }
+
+  int comp[3];
+};
+
+#define COONCOLOR_THRESHOLD 4
+struct CPDF_PatchDrawer {
+  void Draw(int x_scale,
+            int y_scale,
+            int left,
+            int bottom,
+            Coon_Bezier C1,
+            Coon_Bezier C2,
+            Coon_Bezier D1,
+            Coon_Bezier D2) {
+    bool bSmall = C1.Distance() < 2 && C2.Distance() < 2 && D1.Distance() < 2 &&
+                  D2.Distance() < 2;
+    Coon_Color div_colors[4];
+    int d_bottom = 0;
+    int d_left = 0;
+    int d_top = 0;
+    int d_right = 0;
+    if (!div_colors[0].BiInterpol(patch_colors, left, bottom, x_scale,
+                                  y_scale)) {
+      return;
+    }
+    if (!bSmall) {
+      if (!div_colors[1].BiInterpol(patch_colors, left, bottom + 1, x_scale,
+                                    y_scale)) {
+        return;
+      }
+      if (!div_colors[2].BiInterpol(patch_colors, left + 1, bottom + 1, x_scale,
+                                    y_scale)) {
+        return;
+      }
+      if (!div_colors[3].BiInterpol(patch_colors, left + 1, bottom, x_scale,
+                                    y_scale)) {
+        return;
+      }
+      d_bottom = div_colors[3].Distance(div_colors[0]);
+      d_left = div_colors[1].Distance(div_colors[0]);
+      d_top = div_colors[1].Distance(div_colors[2]);
+      d_right = div_colors[2].Distance(div_colors[3]);
+    }
+
+    if (bSmall ||
+        (d_bottom < COONCOLOR_THRESHOLD && d_left < COONCOLOR_THRESHOLD &&
+         d_top < COONCOLOR_THRESHOLD && d_right < COONCOLOR_THRESHOLD)) {
+      std::vector<FX_PATHPOINT>& pPoints = path.GetPoints();
+      C1.GetPoints(pPoints, 0);
+      D2.GetPoints(pPoints, 3);
+      C2.GetPointsReverse(pPoints, 6);
+      D1.GetPointsReverse(pPoints, 9);
+      int fillFlags = FXFILL_WINDING | FXFILL_FULLCOVER;
+      if (bNoPathSmooth)
+        fillFlags |= FXFILL_NOPATHSMOOTH;
+      pDevice->DrawPath(
+          &path, nullptr, nullptr,
+          ArgbEncode(alpha, div_colors[0].comp[0], div_colors[0].comp[1],
+                     div_colors[0].comp[2]),
+          0, fillFlags);
+    } else {
+      if (d_bottom < COONCOLOR_THRESHOLD && d_top < COONCOLOR_THRESHOLD) {
+        Coon_Bezier m1;
+        m1.BezierInterpol(D1, D2, C1, C2);
+        y_scale *= 2;
+        bottom *= 2;
+        Draw(x_scale, y_scale, left, bottom, C1, m1, D1.first_half(),
+             D2.first_half());
+        Draw(x_scale, y_scale, left, bottom + 1, m1, C2, D1.second_half(),
+             D2.second_half());
+      } else if (d_left < COONCOLOR_THRESHOLD &&
+                 d_right < COONCOLOR_THRESHOLD) {
+        Coon_Bezier m2;
+        m2.BezierInterpol(C1, C2, D1, D2);
+        x_scale *= 2;
+        left *= 2;
+        Draw(x_scale, y_scale, left, bottom, C1.first_half(), C2.first_half(),
+             D1, m2);
+        Draw(x_scale, y_scale, left + 1, bottom, C1.second_half(),
+             C2.second_half(), m2, D2);
+      } else {
+        Coon_Bezier m1, m2;
+        m1.BezierInterpol(D1, D2, C1, C2);
+        m2.BezierInterpol(C1, C2, D1, D2);
+        Coon_Bezier m1f = m1.first_half();
+        Coon_Bezier m1s = m1.second_half();
+        Coon_Bezier m2f = m2.first_half();
+        Coon_Bezier m2s = m2.second_half();
+        x_scale *= 2;
+        y_scale *= 2;
+        left *= 2;
+        bottom *= 2;
+        Draw(x_scale, y_scale, left, bottom, C1.first_half(), m1f,
+             D1.first_half(), m2f);
+        Draw(x_scale, y_scale, left, bottom + 1, m1f, C2.first_half(),
+             D1.second_half(), m2s);
+        Draw(x_scale, y_scale, left + 1, bottom, C1.second_half(), m1s, m2f,
+             D2.first_half());
+        Draw(x_scale, y_scale, left + 1, bottom + 1, m1s, C2.second_half(), m2s,
+             D2.second_half());
+      }
+    }
+  }
+
+  int max_delta;
+  CFX_PathData path;
+  CFX_RenderDevice* pDevice;
+  int bNoPathSmooth;
+  int alpha;
+  Coon_Color patch_colors[4];
+};
+
+void DrawCoonPatchMeshes(
+    ShadingType type,
+    const RetainPtr<CFX_DIBitmap>& pBitmap,
+    const CFX_Matrix& mtObject2Bitmap,
+    const CPDF_Stream* pShadingStream,
+    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
+    const RetainPtr<CPDF_ColorSpace>& pCS,
+    bool bNoPathSmooth,
+    int alpha) {
+  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
+  ASSERT(type == kCoonsPatchMeshShading ||
+         type == kTensorProductPatchMeshShading);
+
+  CFX_DefaultRenderDevice device;
+  device.Attach(pBitmap, false, nullptr, false);
+  CPDF_MeshStream stream(type, funcs, pShadingStream, pCS);
+  if (!stream.Load())
+    return;
+
+  CPDF_PatchDrawer patch;
+  patch.alpha = alpha;
+  patch.pDevice = &device;
+  patch.bNoPathSmooth = bNoPathSmooth;
+
+  for (int i = 0; i < 13; i++) {
+    patch.path.AppendPoint(
+        CFX_PointF(), i == 0 ? FXPT_TYPE::MoveTo : FXPT_TYPE::BezierTo, false);
+  }
+
+  CFX_PointF coords[16];
+  int point_count = type == kTensorProductPatchMeshShading ? 16 : 12;
+  while (!stream.BitStream()->IsEOF()) {
+    if (!stream.CanReadFlag())
+      break;
+    uint32_t flag = stream.ReadFlag();
+    int iStartPoint = 0, iStartColor = 0, i = 0;
+    if (flag) {
+      iStartPoint = 4;
+      iStartColor = 2;
+      CFX_PointF tempCoords[4];
+      for (i = 0; i < 4; i++) {
+        tempCoords[i] = coords[(flag * 3 + i) % 12];
+      }
+      memcpy(coords, tempCoords, sizeof(tempCoords));
+      Coon_Color tempColors[2];
+      tempColors[0] = patch.patch_colors[flag];
+      tempColors[1] = patch.patch_colors[(flag + 1) % 4];
+      memcpy(patch.patch_colors, tempColors, sizeof(Coon_Color) * 2);
+    }
+    for (i = iStartPoint; i < point_count; i++) {
+      if (!stream.CanReadCoords())
+        break;
+      coords[i] = mtObject2Bitmap.Transform(stream.ReadCoords());
+    }
+
+    for (i = iStartColor; i < 4; i++) {
+      if (!stream.CanReadColor())
+        break;
+
+      float r;
+      float g;
+      float b;
+      std::tie(r, g, b) = stream.ReadColor();
+
+      patch.patch_colors[i].comp[0] = (int32_t)(r * 255);
+      patch.patch_colors[i].comp[1] = (int32_t)(g * 255);
+      patch.patch_colors[i].comp[2] = (int32_t)(b * 255);
+    }
+    CFX_FloatRect bbox = CFX_FloatRect::GetBBox(coords, point_count);
+    if (bbox.right <= 0 || bbox.left >= (float)pBitmap->GetWidth() ||
+        bbox.top <= 0 || bbox.bottom >= (float)pBitmap->GetHeight()) {
+      continue;
+    }
+    Coon_Bezier C1, C2, D1, D2;
+    C1.FromPoints(coords[0].x, coords[0].y, coords[11].x, coords[11].y,
+                  coords[10].x, coords[10].y, coords[9].x, coords[9].y);
+    C2.FromPoints(coords[3].x, coords[3].y, coords[4].x, coords[4].y,
+                  coords[5].x, coords[5].y, coords[6].x, coords[6].y);
+    D1.FromPoints(coords[0].x, coords[0].y, coords[1].x, coords[1].y,
+                  coords[2].x, coords[2].y, coords[3].x, coords[3].y);
+    D2.FromPoints(coords[9].x, coords[9].y, coords[8].x, coords[8].y,
+                  coords[7].x, coords[7].y, coords[6].x, coords[6].y);
+    patch.Draw(1, 1, 0, 0, C1, C2, D1, D2);
+  }
+}
+
+}  // namespace
+
+// static
+void CPDF_RenderShading::Draw(CFX_RenderDevice* pDevice,
+                              CPDF_RenderContext* pContext,
+                              const CPDF_PageObject* pCurObj,
+                              const CPDF_ShadingPattern* pPattern,
+                              const CFX_Matrix& mtMatrix,
+                              const FX_RECT& clip_rect,
+                              int alpha,
+                              const CPDF_RenderOptions& options) {
+  const auto& funcs = pPattern->GetFuncs();
+  const CPDF_Dictionary* pDict = pPattern->GetShadingObject()->GetDict();
+  RetainPtr<CPDF_ColorSpace> pColorSpace = pPattern->GetCS();
+  if (!pColorSpace)
+    return;
+
+  FX_ARGB background = 0;
+  if (!pPattern->IsShadingObject() && pDict->KeyExist("Background")) {
+    const CPDF_Array* pBackColor = pDict->GetArrayFor("Background");
+    if (pBackColor && pBackColor->size() >= pColorSpace->CountComponents()) {
+      std::vector<float> comps =
+          ReadArrayElementsToVector(pBackColor, pColorSpace->CountComponents());
+
+      float R = 0.0f;
+      float G = 0.0f;
+      float B = 0.0f;
+      pColorSpace->GetRGB(comps.data(), &R, &G, &B);
+      background = ArgbEncode(255, (int32_t)(R * 255), (int32_t)(G * 255),
+                              (int32_t)(B * 255));
+    }
+  }
+  FX_RECT clip_rect_bbox = clip_rect;
+  if (pDict->KeyExist("BBox")) {
+    clip_rect_bbox.Intersect(
+        mtMatrix.TransformRect(pDict->GetRectFor("BBox")).GetOuterRect());
+  }
+  bool bAlphaMode = options.ColorModeIs(CPDF_RenderOptions::kAlpha);
+  if (pDevice->GetDeviceCaps(FXDC_RENDER_CAPS) & FXRC_SHADING &&
+      pDevice->GetDeviceDriver()->DrawShading(
+          pPattern, &mtMatrix, clip_rect_bbox, alpha, bAlphaMode)) {
+    return;
+  }
+  CPDF_DeviceBuffer buffer(pContext, pDevice, clip_rect_bbox, pCurObj, 150);
+  if (!buffer.Initialize())
+    return;
+
+  CFX_Matrix FinalMatrix = mtMatrix * buffer.GetMatrix();
+  RetainPtr<CFX_DIBitmap> pBitmap = buffer.GetBitmap();
+  if (!pBitmap->GetBuffer())
+    return;
+
+  pBitmap->Clear(background);
+  switch (pPattern->GetShadingType()) {
+    case kInvalidShading:
+    case kMaxShading:
+      return;
+    case kFunctionBasedShading:
+      DrawFuncShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
+      break;
+    case kAxialShading:
+      DrawAxialShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
+      break;
+    case kRadialShading:
+      DrawRadialShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
+      break;
+    case kFreeFormGouraudTriangleMeshShading: {
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
+        DrawFreeGouraudShading(pBitmap, FinalMatrix, pStream, funcs,
+                               pColorSpace, alpha);
+      }
+    } break;
+    case kLatticeFormGouraudTriangleMeshShading: {
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
+        DrawLatticeGouraudShading(pBitmap, FinalMatrix, pStream, funcs,
+                                  pColorSpace, alpha);
+      }
+    } break;
+    case kCoonsPatchMeshShading:
+    case kTensorProductPatchMeshShading: {
+      // The shading object can be a stream or a dictionary. We do not handle
+      // the case of dictionary at the moment.
+      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
+        DrawCoonPatchMeshes(pPattern->GetShadingType(), pBitmap, FinalMatrix,
+                            pStream, funcs, pColorSpace,
+                            options.GetOptions().bNoPathSmooth, alpha);
+      }
+    } break;
+  }
+  if (bAlphaMode)
+    pBitmap->LoadChannelFromAlpha(FXDIB_Red, pBitmap);
+
+  if (options.ColorModeIs(CPDF_RenderOptions::kGray))
+    pBitmap->ConvertColorScale(0, 0xffffff);
+  buffer.OutputToDevice();
+}
diff --git a/core/fpdfapi/render/cpdf_rendershading.h b/core/fpdfapi/render/cpdf_rendershading.h
new file mode 100644
index 0000000..8c0d8a4
--- /dev/null
+++ b/core/fpdfapi/render/cpdf_rendershading.h
@@ -0,0 +1,34 @@
+// Copyright 2019 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef CORE_FPDFAPI_RENDER_CPDF_RENDERSHADING_H_
+#define CORE_FPDFAPI_RENDER_CPDF_RENDERSHADING_H_
+
+class CFX_Matrix;
+class CFX_RenderDevice;
+class CPDF_PageObject;
+class CPDF_RenderContext;
+class CPDF_RenderOptions;
+class CPDF_ShadingPattern;
+struct FX_RECT;
+
+class CPDF_RenderShading {
+ public:
+  static void Draw(CFX_RenderDevice* pDevice,
+                   CPDF_RenderContext* pContext,
+                   const CPDF_PageObject* pCurObj,
+                   const CPDF_ShadingPattern* pPattern,
+                   const CFX_Matrix& mtMatrix,
+                   const FX_RECT& clip_rect,
+                   int alpha,
+                   const CPDF_RenderOptions& options);
+
+  CPDF_RenderShading() = delete;
+  CPDF_RenderShading(const CPDF_RenderShading&) = delete;
+  CPDF_RenderShading& operator=(const CPDF_RenderShading&) = delete;
+};
+
+#endif  // CORE_FPDFAPI_RENDER_CPDF_RENDERSHADING_H_
diff --git a/core/fpdfapi/render/cpdf_renderstatus.cpp b/core/fpdfapi/render/cpdf_renderstatus.cpp
index 89b815b..217ad71 100644
--- a/core/fpdfapi/render/cpdf_renderstatus.cpp
+++ b/core/fpdfapi/render/cpdf_renderstatus.cpp
@@ -7,7 +7,6 @@
 #include "core/fpdfapi/render/cpdf_renderstatus.h"
 
 #include <algorithm>
-#include <array>
 #include <cmath>
 #include <limits>
 #include <memory>
@@ -20,7 +19,6 @@
 #include "core/fpdfapi/font/cpdf_font.h"
 #include "core/fpdfapi/font/cpdf_type3char.h"
 #include "core/fpdfapi/font/cpdf_type3font.h"
-#include "core/fpdfapi/page/cpdf_dibbase.h"
 #include "core/fpdfapi/page/cpdf_docpagedata.h"
 #include "core/fpdfapi/page/cpdf_form.h"
 #include "core/fpdfapi/page/cpdf_formobject.h"
@@ -28,7 +26,6 @@
 #include "core/fpdfapi/page/cpdf_graphicstates.h"
 #include "core/fpdfapi/page/cpdf_image.h"
 #include "core/fpdfapi/page/cpdf_imageobject.h"
-#include "core/fpdfapi/page/cpdf_meshstream.h"
 #include "core/fpdfapi/page/cpdf_occontext.h"
 #include "core/fpdfapi/page/cpdf_page.h"
 #include "core/fpdfapi/page/cpdf_pageobject.h"
@@ -43,22 +40,20 @@
 #include "core/fpdfapi/parser/cpdf_stream.h"
 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
 #include "core/fpdfapi/render/cpdf_charposlist.h"
-#include "core/fpdfapi/render/cpdf_devicebuffer.h"
 #include "core/fpdfapi/render/cpdf_docrenderdata.h"
 #include "core/fpdfapi/render/cpdf_imagerenderer.h"
 #include "core/fpdfapi/render/cpdf_pagerendercache.h"
 #include "core/fpdfapi/render/cpdf_rendercontext.h"
 #include "core/fpdfapi/render/cpdf_renderoptions.h"
+#include "core/fpdfapi/render/cpdf_rendershading.h"
 #include "core/fpdfapi/render/cpdf_scaledrenderbuffer.h"
 #include "core/fpdfapi/render/cpdf_textrenderer.h"
 #include "core/fpdfapi/render/cpdf_type3cache.h"
 #include "core/fxcrt/autorestorer.h"
 #include "core/fxcrt/fx_safe_types.h"
 #include "core/fxcrt/fx_system.h"
-#include "core/fxcrt/maybe_owned.h"
 #include "core/fxge/cfx_defaultrenderdevice.h"
 #include "core/fxge/cfx_glyphbitmap.h"
-#include "core/fxge/cfx_graphstatedata.h"
 #include "core/fxge/cfx_pathdata.h"
 #include "core/fxge/dib/cfx_dibitmap.h"
 #include "core/fxge/fx_font.h"
@@ -77,829 +72,9 @@
 
 namespace {
 
-constexpr int kShadingSteps = 256;
 constexpr int kRenderMaxRecursionDepth = 64;
 int g_CurrentRecursionDepth = 0;
 
-uint32_t CountOutputsFromFunctions(
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs) {
-  FX_SAFE_UINT32 total = 0;
-  for (const auto& func : funcs) {
-    if (func)
-      total += func->CountOutputs();
-  }
-  return total.ValueOrDefault(0);
-}
-
-uint32_t GetValidatedOutputsCount(
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-    const RetainPtr<CPDF_ColorSpace>& pCS) {
-  uint32_t funcs_outputs = CountOutputsFromFunctions(funcs);
-  return funcs_outputs ? std::max(funcs_outputs, pCS->CountComponents()) : 0;
-}
-
-std::array<FX_ARGB, kShadingSteps> GetShadingSteps(
-    float t_min,
-    float t_max,
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-    const RetainPtr<CPDF_ColorSpace>& pCS,
-    int alpha,
-    size_t results_count) {
-  ASSERT(results_count >= CountOutputsFromFunctions(funcs));
-  ASSERT(results_count >= pCS->CountComponents());
-  std::array<FX_ARGB, kShadingSteps> shading_steps;
-  std::vector<float> result_array(results_count);
-  float diff = t_max - t_min;
-  for (int i = 0; i < kShadingSteps; ++i) {
-    float input = diff * i / kShadingSteps + t_min;
-    int offset = 0;
-    for (const auto& func : funcs) {
-      if (func) {
-        int nresults = 0;
-        if (func->Call(&input, 1, &result_array[offset], &nresults))
-          offset += nresults;
-      }
-    }
-    float R = 0.0f;
-    float G = 0.0f;
-    float B = 0.0f;
-    pCS->GetRGB(result_array.data(), &R, &G, &B);
-    shading_steps[i] =
-        FXARGB_TODIB(ArgbEncode(alpha, FXSYS_roundf(R * 255),
-                                FXSYS_roundf(G * 255), FXSYS_roundf(B * 255)));
-  }
-  return shading_steps;
-}
-
-void DrawAxialShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
-                      const CFX_Matrix& mtObject2Bitmap,
-                      const CPDF_Dictionary* pDict,
-                      const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-                      const RetainPtr<CPDF_ColorSpace>& pCS,
-                      int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-
-  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
-  if (total_results == 0)
-    return;
-
-  const CPDF_Array* pCoords = pDict->GetArrayFor("Coords");
-  if (!pCoords)
-    return;
-
-  float start_x = pCoords->GetNumberAt(0);
-  float start_y = pCoords->GetNumberAt(1);
-  float end_x = pCoords->GetNumberAt(2);
-  float end_y = pCoords->GetNumberAt(3);
-  float t_min = 0;
-  float t_max = 1.0f;
-  const CPDF_Array* pArray = pDict->GetArrayFor("Domain");
-  if (pArray) {
-    t_min = pArray->GetNumberAt(0);
-    t_max = pArray->GetNumberAt(1);
-  }
-  pArray = pDict->GetArrayFor("Extend");
-  const bool bStartExtend = pArray && pArray->GetBooleanAt(0, false);
-  const bool bEndExtend = pArray && pArray->GetBooleanAt(1, false);
-
-  int width = pBitmap->GetWidth();
-  int height = pBitmap->GetHeight();
-  float x_span = end_x - start_x;
-  float y_span = end_y - start_y;
-  float axis_len_square = (x_span * x_span) + (y_span * y_span);
-
-  std::array<FX_ARGB, kShadingSteps> shading_steps =
-      GetShadingSteps(t_min, t_max, funcs, pCS, alpha, total_results);
-
-  int pitch = pBitmap->GetPitch();
-  CFX_Matrix matrix = mtObject2Bitmap.GetInverse();
-  for (int row = 0; row < height; row++) {
-    uint32_t* dib_buf =
-        reinterpret_cast<uint32_t*>(pBitmap->GetBuffer() + row * pitch);
-    for (int column = 0; column < width; column++) {
-      CFX_PointF pos = matrix.Transform(
-          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
-      float scale =
-          (((pos.x - start_x) * x_span) + ((pos.y - start_y) * y_span)) /
-          axis_len_square;
-      int index = (int32_t)(scale * (kShadingSteps - 1));
-      if (index < 0) {
-        if (!bStartExtend)
-          continue;
-
-        index = 0;
-      } else if (index >= kShadingSteps) {
-        if (!bEndExtend)
-          continue;
-
-        index = kShadingSteps - 1;
-      }
-      dib_buf[column] = shading_steps[index];
-    }
-  }
-}
-
-void DrawRadialShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
-                       const CFX_Matrix& mtObject2Bitmap,
-                       const CPDF_Dictionary* pDict,
-                       const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-                       const RetainPtr<CPDF_ColorSpace>& pCS,
-                       int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-
-  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
-  if (total_results == 0)
-    return;
-
-  const CPDF_Array* pCoords = pDict->GetArrayFor("Coords");
-  if (!pCoords)
-    return;
-
-  float start_x = pCoords->GetNumberAt(0);
-  float start_y = pCoords->GetNumberAt(1);
-  float start_r = pCoords->GetNumberAt(2);
-  float end_x = pCoords->GetNumberAt(3);
-  float end_y = pCoords->GetNumberAt(4);
-  float end_r = pCoords->GetNumberAt(5);
-  float t_min = 0;
-  float t_max = 1.0f;
-  const CPDF_Array* pArray = pDict->GetArrayFor("Domain");
-  if (pArray) {
-    t_min = pArray->GetNumberAt(0);
-    t_max = pArray->GetNumberAt(1);
-  }
-  pArray = pDict->GetArrayFor("Extend");
-  const bool bStartExtend = pArray && pArray->GetBooleanAt(0, false);
-  const bool bEndExtend = pArray && pArray->GetBooleanAt(1, false);
-
-  std::array<FX_ARGB, kShadingSteps> shading_steps =
-      GetShadingSteps(t_min, t_max, funcs, pCS, alpha, total_results);
-
-  const float dx = end_x - start_x;
-  const float dy = end_y - start_y;
-  const float dr = end_r - start_r;
-  const float a = dx * dx + dy * dy - dr * dr;
-  const bool a_is_float_zero = IsFloatZero(a);
-
-  int width = pBitmap->GetWidth();
-  int height = pBitmap->GetHeight();
-  int pitch = pBitmap->GetPitch();
-
-  bool bDecreasing =
-      (dr < 0 && static_cast<int>(sqrt(dx * dx + dy * dy)) < -dr);
-
-  CFX_Matrix matrix = mtObject2Bitmap.GetInverse();
-  for (int row = 0; row < height; row++) {
-    uint32_t* dib_buf =
-        reinterpret_cast<uint32_t*>(pBitmap->GetBuffer() + row * pitch);
-    for (int column = 0; column < width; column++) {
-      CFX_PointF pos = matrix.Transform(
-          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
-      float pos_dx = pos.x - start_x;
-      float pos_dy = pos.y - start_y;
-      float b = -2 * (pos_dx * dx + pos_dy * dy + start_r * dr);
-      float c = pos_dx * pos_dx + pos_dy * pos_dy - start_r * start_r;
-      float s;
-      if (IsFloatZero(b)) {
-        s = sqrt(-c / a);
-      } else if (a_is_float_zero) {
-        s = -c / b;
-      } else {
-        float b2_4ac = (b * b) - 4 * (a * c);
-        if (b2_4ac < 0)
-          continue;
-
-        float root = sqrt(b2_4ac);
-        float s1 = (-b - root) / (2 * a);
-        float s2 = (-b + root) / (2 * a);
-        if (a <= 0)
-          std::swap(s1, s2);
-        if (bDecreasing)
-          s = (s1 >= 0 || bStartExtend) ? s1 : s2;
-        else
-          s = (s2 <= 1.0f || bEndExtend) ? s2 : s1;
-
-        if (start_r + s * dr < 0)
-          continue;
-      }
-
-      int index = static_cast<int32_t>(s * (kShadingSteps - 1));
-      if (index < 0) {
-        if (!bStartExtend)
-          continue;
-        index = 0;
-      } else if (index >= kShadingSteps) {
-        if (!bEndExtend)
-          continue;
-        index = kShadingSteps - 1;
-      }
-      dib_buf[column] = shading_steps[index];
-    }
-  }
-}
-
-void DrawFuncShading(const RetainPtr<CFX_DIBitmap>& pBitmap,
-                     const CFX_Matrix& mtObject2Bitmap,
-                     const CPDF_Dictionary* pDict,
-                     const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-                     const RetainPtr<CPDF_ColorSpace>& pCS,
-                     int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-
-  const uint32_t total_results = GetValidatedOutputsCount(funcs, pCS);
-  if (total_results == 0)
-    return;
-
-  const CPDF_Array* pDomain = pDict->GetArrayFor("Domain");
-  float xmin = 0.0f;
-  float ymin = 0.0f;
-  float xmax = 1.0f;
-  float ymax = 1.0f;
-  if (pDomain) {
-    xmin = pDomain->GetNumberAt(0);
-    xmax = pDomain->GetNumberAt(1);
-    ymin = pDomain->GetNumberAt(2);
-    ymax = pDomain->GetNumberAt(3);
-  }
-  CFX_Matrix mtDomain2Target = pDict->GetMatrixFor("Matrix");
-  CFX_Matrix matrix =
-      mtObject2Bitmap.GetInverse() * mtDomain2Target.GetInverse();
-  int width = pBitmap->GetWidth();
-  int height = pBitmap->GetHeight();
-  int pitch = pBitmap->GetPitch();
-
-  ASSERT(total_results >= CountOutputsFromFunctions(funcs));
-  ASSERT(total_results >= pCS->CountComponents());
-  std::vector<float> result_array(total_results);
-  for (int row = 0; row < height; ++row) {
-    uint32_t* dib_buf = (uint32_t*)(pBitmap->GetBuffer() + row * pitch);
-    for (int column = 0; column < width; column++) {
-      CFX_PointF pos = matrix.Transform(
-          CFX_PointF(static_cast<float>(column), static_cast<float>(row)));
-      if (pos.x < xmin || pos.x > xmax || pos.y < ymin || pos.y > ymax)
-        continue;
-
-      float input[] = {pos.x, pos.y};
-      int offset = 0;
-      for (const auto& func : funcs) {
-        if (func) {
-          int nresults;
-          if (func->Call(input, 2, &result_array[offset], &nresults))
-            offset += nresults;
-        }
-      }
-
-      float R = 0.0f;
-      float G = 0.0f;
-      float B = 0.0f;
-      pCS->GetRGB(result_array.data(), &R, &G, &B);
-      dib_buf[column] = FXARGB_TODIB(ArgbEncode(
-          alpha, (int32_t)(R * 255), (int32_t)(G * 255), (int32_t)(B * 255)));
-    }
-  }
-}
-
-bool GetScanlineIntersect(int y,
-                          const CFX_PointF& first,
-                          const CFX_PointF& second,
-                          float* x) {
-  if (first.y == second.y)
-    return false;
-
-  if (first.y < second.y) {
-    if (y < first.y || y > second.y)
-      return false;
-  } else if (y < second.y || y > first.y) {
-    return false;
-  }
-  *x = first.x + ((second.x - first.x) * (y - first.y) / (second.y - first.y));
-  return true;
-}
-
-void DrawGouraud(const RetainPtr<CFX_DIBitmap>& pBitmap,
-                 int alpha,
-                 CPDF_MeshVertex triangle[3]) {
-  float min_y = triangle[0].position.y;
-  float max_y = triangle[0].position.y;
-  for (int i = 1; i < 3; i++) {
-    min_y = std::min(min_y, triangle[i].position.y);
-    max_y = std::max(max_y, triangle[i].position.y);
-  }
-  if (min_y == max_y)
-    return;
-
-  int min_yi = std::max(static_cast<int>(floor(min_y)), 0);
-  int max_yi = static_cast<int>(ceil(max_y));
-
-  if (max_yi >= pBitmap->GetHeight())
-    max_yi = pBitmap->GetHeight() - 1;
-
-  for (int y = min_yi; y <= max_yi; y++) {
-    int nIntersects = 0;
-    float inter_x[3];
-    float r[3];
-    float g[3];
-    float b[3];
-    for (int i = 0; i < 3; i++) {
-      CPDF_MeshVertex& vertex1 = triangle[i];
-      CPDF_MeshVertex& vertex2 = triangle[(i + 1) % 3];
-      CFX_PointF& position1 = vertex1.position;
-      CFX_PointF& position2 = vertex2.position;
-      bool bIntersect =
-          GetScanlineIntersect(y, position1, position2, &inter_x[nIntersects]);
-      if (!bIntersect)
-        continue;
-
-      float y_dist = (y - position1.y) / (position2.y - position1.y);
-      r[nIntersects] = vertex1.r + ((vertex2.r - vertex1.r) * y_dist);
-      g[nIntersects] = vertex1.g + ((vertex2.g - vertex1.g) * y_dist);
-      b[nIntersects] = vertex1.b + ((vertex2.b - vertex1.b) * y_dist);
-      nIntersects++;
-    }
-    if (nIntersects != 2)
-      continue;
-
-    int min_x, max_x, start_index, end_index;
-    if (inter_x[0] < inter_x[1]) {
-      min_x = (int)floor(inter_x[0]);
-      max_x = (int)ceil(inter_x[1]);
-      start_index = 0;
-      end_index = 1;
-    } else {
-      min_x = (int)floor(inter_x[1]);
-      max_x = (int)ceil(inter_x[0]);
-      start_index = 1;
-      end_index = 0;
-    }
-
-    int start_x = std::max(min_x, 0);
-    int end_x = max_x;
-    if (end_x > pBitmap->GetWidth())
-      end_x = pBitmap->GetWidth();
-
-    uint8_t* dib_buf =
-        pBitmap->GetBuffer() + y * pBitmap->GetPitch() + start_x * 4;
-    float r_unit = (r[end_index] - r[start_index]) / (max_x - min_x);
-    float g_unit = (g[end_index] - g[start_index]) / (max_x - min_x);
-    float b_unit = (b[end_index] - b[start_index]) / (max_x - min_x);
-    float R = r[start_index] + (start_x - min_x) * r_unit;
-    float G = g[start_index] + (start_x - min_x) * g_unit;
-    float B = b[start_index] + (start_x - min_x) * b_unit;
-    for (int x = start_x; x < end_x; x++) {
-      R += r_unit;
-      G += g_unit;
-      B += b_unit;
-      FXARGB_SETDIB(dib_buf,
-                    ArgbEncode(alpha, (int32_t)(R * 255), (int32_t)(G * 255),
-                               (int32_t)(B * 255)));
-      dib_buf += 4;
-    }
-  }
-}
-
-void DrawFreeGouraudShading(
-    const RetainPtr<CFX_DIBitmap>& pBitmap,
-    const CFX_Matrix& mtObject2Bitmap,
-    const CPDF_Stream* pShadingStream,
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-    const RetainPtr<CPDF_ColorSpace>& pCS,
-    int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-
-  CPDF_MeshStream stream(kFreeFormGouraudTriangleMeshShading, funcs,
-                         pShadingStream, pCS);
-  if (!stream.Load())
-    return;
-
-  CPDF_MeshVertex triangle[3];
-  memset(triangle, 0, sizeof(triangle));
-
-  while (!stream.BitStream()->IsEOF()) {
-    CPDF_MeshVertex vertex;
-    uint32_t flag;
-    if (!stream.ReadVertex(mtObject2Bitmap, &vertex, &flag))
-      return;
-
-    if (flag == 0) {
-      triangle[0] = vertex;
-      for (int j = 1; j < 3; j++) {
-        uint32_t tflag;
-        if (!stream.ReadVertex(mtObject2Bitmap, &triangle[j], &tflag))
-          return;
-      }
-    } else {
-      if (flag == 1)
-        triangle[0] = triangle[1];
-
-      triangle[1] = triangle[2];
-      triangle[2] = vertex;
-    }
-    DrawGouraud(pBitmap, alpha, triangle);
-  }
-}
-
-void DrawLatticeGouraudShading(
-    const RetainPtr<CFX_DIBitmap>& pBitmap,
-    const CFX_Matrix& mtObject2Bitmap,
-    const CPDF_Stream* pShadingStream,
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-    const RetainPtr<CPDF_ColorSpace>& pCS,
-    int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-
-  int row_verts = pShadingStream->GetDict()->GetIntegerFor("VerticesPerRow");
-  if (row_verts < 2)
-    return;
-
-  CPDF_MeshStream stream(kLatticeFormGouraudTriangleMeshShading, funcs,
-                         pShadingStream, pCS);
-  if (!stream.Load())
-    return;
-
-  std::vector<CPDF_MeshVertex> vertices[2];
-  vertices[0] = stream.ReadVertexRow(mtObject2Bitmap, row_verts);
-  if (vertices[0].empty())
-    return;
-
-  int last_index = 0;
-  while (1) {
-    vertices[1 - last_index] = stream.ReadVertexRow(mtObject2Bitmap, row_verts);
-    if (vertices[1 - last_index].empty())
-      return;
-
-    CPDF_MeshVertex triangle[3];
-    for (int i = 1; i < row_verts; ++i) {
-      triangle[0] = vertices[last_index][i];
-      triangle[1] = vertices[1 - last_index][i - 1];
-      triangle[2] = vertices[last_index][i - 1];
-      DrawGouraud(pBitmap, alpha, triangle);
-      triangle[2] = vertices[1 - last_index][i];
-      DrawGouraud(pBitmap, alpha, triangle);
-    }
-    last_index = 1 - last_index;
-  }
-}
-
-struct Coon_BezierCoeff {
-  float a, b, c, d;
-  void FromPoints(float p0, float p1, float p2, float p3) {
-    a = -p0 + 3 * p1 - 3 * p2 + p3;
-    b = 3 * p0 - 6 * p1 + 3 * p2;
-    c = -3 * p0 + 3 * p1;
-    d = p0;
-  }
-  Coon_BezierCoeff first_half() {
-    Coon_BezierCoeff result;
-    result.a = a / 8;
-    result.b = b / 4;
-    result.c = c / 2;
-    result.d = d;
-    return result;
-  }
-  Coon_BezierCoeff second_half() {
-    Coon_BezierCoeff result;
-    result.a = a / 8;
-    result.b = 3 * a / 8 + b / 4;
-    result.c = 3 * a / 8 + b / 2 + c / 2;
-    result.d = a / 8 + b / 4 + c / 2 + d;
-    return result;
-  }
-  void GetPoints(float p[4]) {
-    p[0] = d;
-    p[1] = c / 3 + p[0];
-    p[2] = b / 3 - p[0] + 2 * p[1];
-    p[3] = a + p[0] - 3 * p[1] + 3 * p[2];
-  }
-  void GetPointsReverse(float p[4]) {
-    p[3] = d;
-    p[2] = c / 3 + p[3];
-    p[1] = b / 3 - p[3] + 2 * p[2];
-    p[0] = a + p[3] - 3 * p[2] + 3 * p[1];
-  }
-  void BezierInterpol(Coon_BezierCoeff& C1,
-                      Coon_BezierCoeff& C2,
-                      Coon_BezierCoeff& D1,
-                      Coon_BezierCoeff& D2) {
-    a = (D1.a + D2.a) / 2;
-    b = (D1.b + D2.b) / 2;
-    c = (D1.c + D2.c) / 2 - (C1.a / 8 + C1.b / 4 + C1.c / 2) +
-        (C2.a / 8 + C2.b / 4) + (-C1.d + D2.d) / 2 - (C2.a + C2.b) / 2;
-    d = C1.a / 8 + C1.b / 4 + C1.c / 2 + C1.d;
-  }
-  float Distance() {
-    float dis = a + b + c;
-    return dis < 0 ? -dis : dis;
-  }
-};
-
-struct Coon_Bezier {
-  Coon_BezierCoeff x, y;
-  void FromPoints(float x0,
-                  float y0,
-                  float x1,
-                  float y1,
-                  float x2,
-                  float y2,
-                  float x3,
-                  float y3) {
-    x.FromPoints(x0, x1, x2, x3);
-    y.FromPoints(y0, y1, y2, y3);
-  }
-
-  Coon_Bezier first_half() {
-    Coon_Bezier result;
-    result.x = x.first_half();
-    result.y = y.first_half();
-    return result;
-  }
-
-  Coon_Bezier second_half() {
-    Coon_Bezier result;
-    result.x = x.second_half();
-    result.y = y.second_half();
-    return result;
-  }
-
-  void BezierInterpol(Coon_Bezier& C1,
-                      Coon_Bezier& C2,
-                      Coon_Bezier& D1,
-                      Coon_Bezier& D2) {
-    x.BezierInterpol(C1.x, C2.x, D1.x, D2.x);
-    y.BezierInterpol(C1.y, C2.y, D1.y, D2.y);
-  }
-
-  void GetPoints(std::vector<FX_PATHPOINT>& pPoints, size_t start_idx) {
-    float p[4];
-    int i;
-    x.GetPoints(p);
-    for (i = 0; i < 4; i++)
-      pPoints[start_idx + i].m_Point.x = p[i];
-
-    y.GetPoints(p);
-    for (i = 0; i < 4; i++)
-      pPoints[start_idx + i].m_Point.y = p[i];
-  }
-
-  void GetPointsReverse(std::vector<FX_PATHPOINT>& pPoints, size_t start_idx) {
-    float p[4];
-    int i;
-    x.GetPointsReverse(p);
-    for (i = 0; i < 4; i++)
-      pPoints[i + start_idx].m_Point.x = p[i];
-
-    y.GetPointsReverse(p);
-    for (i = 0; i < 4; i++)
-      pPoints[i + start_idx].m_Point.y = p[i];
-  }
-
-  float Distance() { return x.Distance() + y.Distance(); }
-};
-
-int Interpolate(int p1, int p2, int delta1, int delta2, bool* overflow) {
-  pdfium::base::CheckedNumeric<int> p = p2;
-  p -= p1;
-  p *= delta1;
-  p /= delta2;
-  p += p1;
-  if (!p.IsValid())
-    *overflow = true;
-  return p.ValueOrDefault(0);
-}
-
-int BiInterpolImpl(int c0,
-                   int c1,
-                   int c2,
-                   int c3,
-                   int x,
-                   int y,
-                   int x_scale,
-                   int y_scale,
-                   bool* overflow) {
-  int x1 = Interpolate(c0, c3, x, x_scale, overflow);
-  int x2 = Interpolate(c1, c2, x, x_scale, overflow);
-  return Interpolate(x1, x2, y, y_scale, overflow);
-}
-
-struct Coon_Color {
-  Coon_Color() { memset(comp, 0, sizeof(int) * 3); }
-
-  // Returns true if successful, false if overflow detected.
-  bool BiInterpol(Coon_Color colors[4],
-                  int x,
-                  int y,
-                  int x_scale,
-                  int y_scale) {
-    bool overflow = false;
-    for (int i = 0; i < 3; i++) {
-      comp[i] = BiInterpolImpl(colors[0].comp[i], colors[1].comp[i],
-                               colors[2].comp[i], colors[3].comp[i], x, y,
-                               x_scale, y_scale, &overflow);
-    }
-    return !overflow;
-  }
-
-  int Distance(Coon_Color& o) {
-    return std::max({abs(comp[0] - o.comp[0]), abs(comp[1] - o.comp[1]),
-                     abs(comp[2] - o.comp[2])});
-  }
-
-  int comp[3];
-};
-
-#define COONCOLOR_THRESHOLD 4
-struct CPDF_PatchDrawer {
-  void Draw(int x_scale,
-            int y_scale,
-            int left,
-            int bottom,
-            Coon_Bezier C1,
-            Coon_Bezier C2,
-            Coon_Bezier D1,
-            Coon_Bezier D2) {
-    bool bSmall = C1.Distance() < 2 && C2.Distance() < 2 && D1.Distance() < 2 &&
-                  D2.Distance() < 2;
-    Coon_Color div_colors[4];
-    int d_bottom = 0;
-    int d_left = 0;
-    int d_top = 0;
-    int d_right = 0;
-    if (!div_colors[0].BiInterpol(patch_colors, left, bottom, x_scale,
-                                  y_scale)) {
-      return;
-    }
-    if (!bSmall) {
-      if (!div_colors[1].BiInterpol(patch_colors, left, bottom + 1, x_scale,
-                                    y_scale)) {
-        return;
-      }
-      if (!div_colors[2].BiInterpol(patch_colors, left + 1, bottom + 1, x_scale,
-                                    y_scale)) {
-        return;
-      }
-      if (!div_colors[3].BiInterpol(patch_colors, left + 1, bottom, x_scale,
-                                    y_scale)) {
-        return;
-      }
-      d_bottom = div_colors[3].Distance(div_colors[0]);
-      d_left = div_colors[1].Distance(div_colors[0]);
-      d_top = div_colors[1].Distance(div_colors[2]);
-      d_right = div_colors[2].Distance(div_colors[3]);
-    }
-
-    if (bSmall ||
-        (d_bottom < COONCOLOR_THRESHOLD && d_left < COONCOLOR_THRESHOLD &&
-         d_top < COONCOLOR_THRESHOLD && d_right < COONCOLOR_THRESHOLD)) {
-      std::vector<FX_PATHPOINT>& pPoints = path.GetPoints();
-      C1.GetPoints(pPoints, 0);
-      D2.GetPoints(pPoints, 3);
-      C2.GetPointsReverse(pPoints, 6);
-      D1.GetPointsReverse(pPoints, 9);
-      int fillFlags = FXFILL_WINDING | FXFILL_FULLCOVER;
-      if (bNoPathSmooth)
-        fillFlags |= FXFILL_NOPATHSMOOTH;
-      pDevice->DrawPath(
-          &path, nullptr, nullptr,
-          ArgbEncode(alpha, div_colors[0].comp[0], div_colors[0].comp[1],
-                     div_colors[0].comp[2]),
-          0, fillFlags);
-    } else {
-      if (d_bottom < COONCOLOR_THRESHOLD && d_top < COONCOLOR_THRESHOLD) {
-        Coon_Bezier m1;
-        m1.BezierInterpol(D1, D2, C1, C2);
-        y_scale *= 2;
-        bottom *= 2;
-        Draw(x_scale, y_scale, left, bottom, C1, m1, D1.first_half(),
-             D2.first_half());
-        Draw(x_scale, y_scale, left, bottom + 1, m1, C2, D1.second_half(),
-             D2.second_half());
-      } else if (d_left < COONCOLOR_THRESHOLD &&
-                 d_right < COONCOLOR_THRESHOLD) {
-        Coon_Bezier m2;
-        m2.BezierInterpol(C1, C2, D1, D2);
-        x_scale *= 2;
-        left *= 2;
-        Draw(x_scale, y_scale, left, bottom, C1.first_half(), C2.first_half(),
-             D1, m2);
-        Draw(x_scale, y_scale, left + 1, bottom, C1.second_half(),
-             C2.second_half(), m2, D2);
-      } else {
-        Coon_Bezier m1, m2;
-        m1.BezierInterpol(D1, D2, C1, C2);
-        m2.BezierInterpol(C1, C2, D1, D2);
-        Coon_Bezier m1f = m1.first_half();
-        Coon_Bezier m1s = m1.second_half();
-        Coon_Bezier m2f = m2.first_half();
-        Coon_Bezier m2s = m2.second_half();
-        x_scale *= 2;
-        y_scale *= 2;
-        left *= 2;
-        bottom *= 2;
-        Draw(x_scale, y_scale, left, bottom, C1.first_half(), m1f,
-             D1.first_half(), m2f);
-        Draw(x_scale, y_scale, left, bottom + 1, m1f, C2.first_half(),
-             D1.second_half(), m2s);
-        Draw(x_scale, y_scale, left + 1, bottom, C1.second_half(), m1s, m2f,
-             D2.first_half());
-        Draw(x_scale, y_scale, left + 1, bottom + 1, m1s, C2.second_half(), m2s,
-             D2.second_half());
-      }
-    }
-  }
-
-  int max_delta;
-  CFX_PathData path;
-  CFX_RenderDevice* pDevice;
-  int bNoPathSmooth;
-  int alpha;
-  Coon_Color patch_colors[4];
-};
-
-void DrawCoonPatchMeshes(
-    ShadingType type,
-    const RetainPtr<CFX_DIBitmap>& pBitmap,
-    const CFX_Matrix& mtObject2Bitmap,
-    const CPDF_Stream* pShadingStream,
-    const std::vector<std::unique_ptr<CPDF_Function>>& funcs,
-    const RetainPtr<CPDF_ColorSpace>& pCS,
-    bool bNoPathSmooth,
-    int alpha) {
-  ASSERT(pBitmap->GetFormat() == FXDIB_Argb);
-  ASSERT(type == kCoonsPatchMeshShading ||
-         type == kTensorProductPatchMeshShading);
-
-  CFX_DefaultRenderDevice device;
-  device.Attach(pBitmap, false, nullptr, false);
-  CPDF_MeshStream stream(type, funcs, pShadingStream, pCS);
-  if (!stream.Load())
-    return;
-
-  CPDF_PatchDrawer patch;
-  patch.alpha = alpha;
-  patch.pDevice = &device;
-  patch.bNoPathSmooth = bNoPathSmooth;
-
-  for (int i = 0; i < 13; i++) {
-    patch.path.AppendPoint(
-        CFX_PointF(), i == 0 ? FXPT_TYPE::MoveTo : FXPT_TYPE::BezierTo, false);
-  }
-
-  CFX_PointF coords[16];
-  int point_count = type == kTensorProductPatchMeshShading ? 16 : 12;
-  while (!stream.BitStream()->IsEOF()) {
-    if (!stream.CanReadFlag())
-      break;
-    uint32_t flag = stream.ReadFlag();
-    int iStartPoint = 0, iStartColor = 0, i = 0;
-    if (flag) {
-      iStartPoint = 4;
-      iStartColor = 2;
-      CFX_PointF tempCoords[4];
-      for (i = 0; i < 4; i++) {
-        tempCoords[i] = coords[(flag * 3 + i) % 12];
-      }
-      memcpy(coords, tempCoords, sizeof(tempCoords));
-      Coon_Color tempColors[2];
-      tempColors[0] = patch.patch_colors[flag];
-      tempColors[1] = patch.patch_colors[(flag + 1) % 4];
-      memcpy(patch.patch_colors, tempColors, sizeof(Coon_Color) * 2);
-    }
-    for (i = iStartPoint; i < point_count; i++) {
-      if (!stream.CanReadCoords())
-        break;
-      coords[i] = mtObject2Bitmap.Transform(stream.ReadCoords());
-    }
-
-    for (i = iStartColor; i < 4; i++) {
-      if (!stream.CanReadColor())
-        break;
-
-      float r;
-      float g;
-      float b;
-      std::tie(r, g, b) = stream.ReadColor();
-
-      patch.patch_colors[i].comp[0] = (int32_t)(r * 255);
-      patch.patch_colors[i].comp[1] = (int32_t)(g * 255);
-      patch.patch_colors[i].comp[2] = (int32_t)(b * 255);
-    }
-    CFX_FloatRect bbox = CFX_FloatRect::GetBBox(coords, point_count);
-    if (bbox.right <= 0 || bbox.left >= (float)pBitmap->GetWidth() ||
-        bbox.top <= 0 || bbox.bottom >= (float)pBitmap->GetHeight()) {
-      continue;
-    }
-    Coon_Bezier C1, C2, D1, D2;
-    C1.FromPoints(coords[0].x, coords[0].y, coords[11].x, coords[11].y,
-                  coords[10].x, coords[10].y, coords[9].x, coords[9].y);
-    C2.FromPoints(coords[3].x, coords[3].y, coords[4].x, coords[4].y,
-                  coords[5].x, coords[5].y, coords[6].x, coords[6].y);
-    D1.FromPoints(coords[0].x, coords[0].y, coords[1].x, coords[1].y,
-                  coords[2].x, coords[2].y, coords[3].x, coords[3].y);
-    D2.FromPoints(coords[9].x, coords[9].y, coords[8].x, coords[8].y,
-                  coords[7].x, coords[7].y, coords[6].x, coords[6].y);
-    patch.Draw(1, 1, 0, 0, C1, C2, D1, D2);
-  }
-}
-
 RetainPtr<CFX_DIBitmap> DrawPatternBitmap(
     CPDF_Document* pDoc,
     CPDF_PageRenderCache* pCache,
@@ -1995,101 +1170,6 @@
   }
 }
 
-void CPDF_RenderStatus::DrawShading(const CPDF_ShadingPattern* pPattern,
-                                    const CFX_Matrix& mtMatrix,
-                                    const FX_RECT& clip_rect,
-                                    int alpha,
-                                    bool bAlphaMode) {
-  const auto& funcs = pPattern->GetFuncs();
-  const CPDF_Dictionary* pDict = pPattern->GetShadingObject()->GetDict();
-  RetainPtr<CPDF_ColorSpace> pColorSpace = pPattern->GetCS();
-  if (!pColorSpace)
-    return;
-
-  FX_ARGB background = 0;
-  if (!pPattern->IsShadingObject() && pDict->KeyExist("Background")) {
-    const CPDF_Array* pBackColor = pDict->GetArrayFor("Background");
-    if (pBackColor && pBackColor->size() >= pColorSpace->CountComponents()) {
-      std::vector<float> comps =
-          ReadArrayElementsToVector(pBackColor, pColorSpace->CountComponents());
-
-      float R = 0.0f;
-      float G = 0.0f;
-      float B = 0.0f;
-      pColorSpace->GetRGB(comps.data(), &R, &G, &B);
-      background = ArgbEncode(255, (int32_t)(R * 255), (int32_t)(G * 255),
-                              (int32_t)(B * 255));
-    }
-  }
-  FX_RECT clip_rect_bbox = clip_rect;
-  if (pDict->KeyExist("BBox")) {
-    clip_rect_bbox.Intersect(
-        mtMatrix.TransformRect(pDict->GetRectFor("BBox")).GetOuterRect());
-  }
-  if (m_pDevice->GetDeviceCaps(FXDC_RENDER_CAPS) & FXRC_SHADING &&
-      m_pDevice->GetDeviceDriver()->DrawShading(
-          pPattern, &mtMatrix, clip_rect_bbox, alpha, bAlphaMode)) {
-    return;
-  }
-  CPDF_DeviceBuffer buffer(m_pContext.Get(), m_pDevice, clip_rect_bbox,
-                           m_pCurObj.Get(), 150);
-  if (!buffer.Initialize())
-    return;
-
-  CFX_Matrix FinalMatrix = mtMatrix * buffer.GetMatrix();
-  RetainPtr<CFX_DIBitmap> pBitmap = buffer.GetBitmap();
-  if (!pBitmap->GetBuffer())
-    return;
-
-  pBitmap->Clear(background);
-  switch (pPattern->GetShadingType()) {
-    case kInvalidShading:
-    case kMaxShading:
-      return;
-    case kFunctionBasedShading:
-      DrawFuncShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
-      break;
-    case kAxialShading:
-      DrawAxialShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
-      break;
-    case kRadialShading:
-      DrawRadialShading(pBitmap, FinalMatrix, pDict, funcs, pColorSpace, alpha);
-      break;
-    case kFreeFormGouraudTriangleMeshShading: {
-      // The shading object can be a stream or a dictionary. We do not handle
-      // the case of dictionary at the moment.
-      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
-        DrawFreeGouraudShading(pBitmap, FinalMatrix, pStream, funcs,
-                               pColorSpace, alpha);
-      }
-    } break;
-    case kLatticeFormGouraudTriangleMeshShading: {
-      // The shading object can be a stream or a dictionary. We do not handle
-      // the case of dictionary at the moment.
-      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
-        DrawLatticeGouraudShading(pBitmap, FinalMatrix, pStream, funcs,
-                                  pColorSpace, alpha);
-      }
-    } break;
-    case kCoonsPatchMeshShading:
-    case kTensorProductPatchMeshShading: {
-      // The shading object can be a stream or a dictionary. We do not handle
-      // the case of dictionary at the moment.
-      if (const CPDF_Stream* pStream = ToStream(pPattern->GetShadingObject())) {
-        DrawCoonPatchMeshes(pPattern->GetShadingType(), pBitmap, FinalMatrix,
-                            pStream, funcs, pColorSpace,
-                            m_Options.GetOptions().bNoPathSmooth, alpha);
-      }
-    } break;
-  }
-  if (bAlphaMode)
-    pBitmap->LoadChannelFromAlpha(FXDIB_Red, pBitmap);
-
-  if (m_Options.ColorModeIs(CPDF_RenderOptions::kGray))
-    pBitmap->ConvertColorScale(0, 0xffffff);
-  buffer.OutputToDevice();
-}
-
 void CPDF_RenderStatus::DrawShadingPattern(CPDF_ShadingPattern* pattern,
                                            const CPDF_PageObject* pPageObj,
                                            const CFX_Matrix& mtObj2Device,
@@ -2109,8 +1189,8 @@
   int alpha =
       FXSYS_roundf(255 * (bStroke ? pPageObj->m_GeneralState.GetStrokeAlpha()
                                   : pPageObj->m_GeneralState.GetFillAlpha()));
-  DrawShading(pattern, matrix, rect, alpha,
-              m_Options.ColorModeIs(CPDF_RenderOptions::kAlpha));
+  CPDF_RenderShading::Draw(m_pDevice, m_pContext.Get(), m_pCurObj.Get(),
+                           pattern, matrix, rect, alpha, m_Options);
 }
 
 void CPDF_RenderStatus::ProcessShading(const CPDF_ShadingObject* pShadingObj,
@@ -2122,9 +1202,11 @@
     return;
 
   CFX_Matrix matrix = pShadingObj->matrix() * mtObj2Device;
-  DrawShading(pShadingObj->pattern(), matrix, rect,
-              FXSYS_roundf(255 * pShadingObj->m_GeneralState.GetFillAlpha()),
-              m_Options.ColorModeIs(CPDF_RenderOptions::kAlpha));
+  CPDF_RenderShading::Draw(
+      m_pDevice, m_pContext.Get(), m_pCurObj.Get(), pShadingObj->pattern(),
+      matrix, rect,
+      FXSYS_roundf(255 * pShadingObj->m_GeneralState.GetFillAlpha()),
+      m_Options);
 }
 
 void CPDF_RenderStatus::DrawTilingPattern(CPDF_TilingPattern* pPattern,
diff --git a/core/fpdfapi/render/cpdf_renderstatus.h b/core/fpdfapi/render/cpdf_renderstatus.h
index 193a7d3..76eb71c 100644
--- a/core/fpdfapi/render/cpdf_renderstatus.h
+++ b/core/fpdfapi/render/cpdf_renderstatus.h
@@ -152,11 +152,6 @@
                     const CFX_Matrix& mtObj2Device);
   void ProcessShading(const CPDF_ShadingObject* pShadingObj,
                       const CFX_Matrix& mtObj2Device);
-  void DrawShading(const CPDF_ShadingPattern* pPattern,
-                   const CFX_Matrix& mtMatrix,
-                   const FX_RECT& clip_rect,
-                   int alpha,
-                   bool bAlphaMode);
   bool ProcessType3Text(CPDF_TextObject* textobj,
                         const CFX_Matrix& mtObj2Device);
   bool ProcessText(CPDF_TextObject* textobj,