core/fxge/dib/cfx_dibitmap.cpp

// Copyright 2017 The PDFium Authors
// 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/fxge/dib/cfx_dibitmap.h"

#include <limits>
#include <memory>
#include <utility>

#include "build/build_config.h"
#include "core/fxcrt/check.h"
#include "core/fxcrt/check_op.h"
#include "core/fxcrt/compiler_specific.h"
#include "core/fxcrt/data_vector.h"
#include "core/fxcrt/fx_coordinates.h"
#include "core/fxcrt/fx_memcpy_wrappers.h"
#include "core/fxcrt/fx_safe_types.h"
#include "core/fxcrt/notreached.h"
#include "core/fxcrt/numerics/safe_conversions.h"
#include "core/fxcrt/span.h"
#include "core/fxcrt/span_util.h"
#include "core/fxcrt/stl_util.h"
#include "core/fxge/calculate_pitch.h"
#include "core/fxge/cfx_cliprgn.h"
#include "core/fxge/cfx_defaultrenderdevice.h"
#include "core/fxge/dib/cfx_scanlinecompositor.h"

CFX_DIBitmap::CFX_DIBitmap() = default;

bool CFX_DIBitmap::Create(int width, int height, FXDIB_Format format) {
  return Create(width, height, format, nullptr, 0);
}

bool CFX_DIBitmap::Create(int width,
                          int height,
                          FXDIB_Format format,
                          uint8_t* pBuffer,
                          uint32_t pitch) {
  m_pBuffer = nullptr;
  SetFormat(format);
  SetWidth(0);
  SetHeight(0);
  SetPitch(0);

  std::optional<PitchAndSize> pitch_size =
      CalculatePitchAndSize(width, height, format, pitch);
  if (!pitch_size.has_value())
    return false;

  if (pBuffer) {
    m_pBuffer.Reset(pBuffer);
  } else {
    FX_SAFE_SIZE_T safe_buffer_size = pitch_size.value().size;
    safe_buffer_size += 4;
    if (!safe_buffer_size.IsValid())
      return false;

    m_pBuffer = std::unique_ptr<uint8_t, FxFreeDeleter>(
        FX_TryAlloc(uint8_t, safe_buffer_size.ValueOrDie()));
    if (!m_pBuffer)
      return false;
  }
  SetWidth(width);
  SetHeight(height);
  SetPitch(pitch_size.value().pitch);
  return true;
}

bool CFX_DIBitmap::Copy(RetainPtr<const CFX_DIBBase> source) {
  if (m_pBuffer)
    return false;

  if (!Create(source->GetWidth(), source->GetHeight(), source->GetFormat())) {
    return false;
  }

  SetPalette(source->GetPaletteSpan());
  for (int row = 0; row < source->GetHeight(); row++) {
    UNSAFE_TODO(FXSYS_memcpy(m_pBuffer.Get() + row * GetPitch(),
                             source->GetScanline(row).data(), GetPitch()));
  }
  return true;
}

CFX_DIBitmap::~CFX_DIBitmap() = default;

pdfium::span<const uint8_t> CFX_DIBitmap::GetBuffer() const {
  if (!m_pBuffer)
    return pdfium::span<const uint8_t>();

  return UNSAFE_TODO(
      pdfium::make_span(m_pBuffer.Get(), GetHeight() * GetPitch()));
}

pdfium::span<const uint8_t> CFX_DIBitmap::GetScanline(int line) const {
  auto buffer_span = GetBuffer();
  if (buffer_span.empty())
    return pdfium::span<const uint8_t>();

  return buffer_span.subspan(line * GetPitch(), GetPitch());
}

size_t CFX_DIBitmap::GetEstimatedImageMemoryBurden() const {
  size_t result = CFX_DIBBase::GetEstimatedImageMemoryBurden();
  if (!GetBuffer().empty()) {
    int height = GetHeight();
    CHECK(pdfium::IsValueInRangeForNumericType<size_t>(height));
    result += static_cast<size_t>(height) * GetPitch();
  }
  return result;
}

#if BUILDFLAG(IS_WIN) || defined(PDF_USE_SKIA)
RetainPtr<const CFX_DIBitmap> CFX_DIBitmap::RealizeIfNeeded() const {
  if (GetBuffer().empty()) {
    return Realize();
  }
  return pdfium::WrapRetain(this);
}
#endif

void CFX_DIBitmap::TakeOver(RetainPtr<CFX_DIBitmap>&& pSrcBitmap) {
  m_pBuffer = std::move(pSrcBitmap->m_pBuffer);
  m_palette = std::move(pSrcBitmap->m_palette);
  pSrcBitmap->m_pBuffer = nullptr;
  SetFormat(pSrcBitmap->GetFormat());
  SetWidth(pSrcBitmap->GetWidth());
  SetHeight(pSrcBitmap->GetHeight());
  SetPitch(pSrcBitmap->GetPitch());
}

void CFX_DIBitmap::Clear(uint32_t color) {
  auto buffer = GetWritableBuffer();
  if (buffer.empty()) {
    return;
  }

  switch (GetFormat()) {
    case FXDIB_Format::kInvalid:
      break;
    case FXDIB_Format::k1bppMask:
      fxcrt::Fill(buffer, (color & 0xff000000) ? 0xff : 0);
      break;
    case FXDIB_Format::k1bppRgb:
      fxcrt::Fill(buffer, FindPalette(color) ? 0xff : 0);
      break;
    case FXDIB_Format::k8bppMask:
      fxcrt::Fill(buffer, color >> 24);
      break;
    case FXDIB_Format::k8bppRgb:
      fxcrt::Fill(buffer, FindPalette(color));
      break;
    case FXDIB_Format::kRgb: {
      const FX_BGR_STRUCT<uint8_t> bgr = ArgbToBGRStruct(color);
      if (bgr.red == bgr.green && bgr.green == bgr.blue) {
        fxcrt::Fill(buffer, bgr.red);
      } else {
        for (int row = 0; row < GetHeight(); row++) {
          fxcrt::Fill(GetWritableScanlineAs<FX_BGR_STRUCT<uint8_t>>(row), bgr);
        }
      }
      break;
    }
    case FXDIB_Format::kRgb32:
      if (CFX_DefaultRenderDevice::UseSkiaRenderer()) {
        // TODO(crbug.com/pdfium/2016): This is not reliable because alpha may
        // be modified outside of this operation.
        color |= 0xFF000000;
      }
      [[fallthrough]];
    case FXDIB_Format::kArgb:
      for (int row = 0; row < GetHeight(); row++) {
        fxcrt::Fill(GetWritableScanlineAs<uint32_t>(row), color);
      }
      break;
  }
}

bool CFX_DIBitmap::TransferBitmap(int dest_left,
                                  int dest_top,
                                  int width,
                                  int height,
                                  RetainPtr<const CFX_DIBBase> source,
                                  int src_left,
                                  int src_top) {
  if (!m_pBuffer)
    return false;

  if (!GetOverlapRect(dest_left, dest_top, width, height, source->GetWidth(),
                      source->GetHeight(), src_left, src_top, nullptr)) {
    return true;
  }

  FXDIB_Format dest_format = GetFormat();
  FXDIB_Format src_format = source->GetFormat();
  if (dest_format != src_format) {
    return TransferWithUnequalFormats(dest_format, dest_left, dest_top, width,
                                      height, std::move(source), src_left,
                                      src_top);
  }

  if (GetBPP() != 1) {
    TransferWithMultipleBPP(dest_left, dest_top, width, height,
                            std::move(source), src_left, src_top);
    return true;
  }

  TransferEqualFormatsOneBPP(dest_left, dest_top, width, height,
                             std::move(source), src_left, src_top);
  return true;
}

bool CFX_DIBitmap::TransferWithUnequalFormats(
    FXDIB_Format dest_format,
    int dest_left,
    int dest_top,
    int width,
    int height,
    RetainPtr<const CFX_DIBBase> source,
    int src_left,
    int src_top) {
  if (HasPalette())
    return false;

  if (GetBPP() == 8) {
    dest_format = FXDIB_Format::k8bppMask;
  }

  FX_SAFE_UINT32 offset = dest_left;
  offset *= GetBPP();
  offset /= 8;
  if (!offset.IsValid())
    return false;

  pdfium::span<uint8_t> dest_buf = GetWritableBuffer().subspan(
      dest_top * GetPitch() + static_cast<uint32_t>(offset.ValueOrDie()));
  DataVector<uint32_t> dest_palette =
      ConvertBuffer(dest_format, dest_buf, GetPitch(), width, height, source,
                    src_left, src_top);
  CHECK(dest_palette.empty());
  return true;
}

void CFX_DIBitmap::TransferWithMultipleBPP(int dest_left,
                                           int dest_top,
                                           int width,
                                           int height,
                                           RetainPtr<const CFX_DIBBase> source,
                                           int src_left,
                                           int src_top) {
  int Bpp = GetBPP() / 8;
  UNSAFE_TODO({
    for (int row = 0; row < height; ++row) {
      uint8_t* dest_scan =
          m_pBuffer.Get() + (dest_top + row) * GetPitch() + dest_left * Bpp;
      const uint8_t* src_scan =
          source->GetScanline(src_top + row).subspan(src_left * Bpp).data();
      FXSYS_memcpy(dest_scan, src_scan, width * Bpp);
    }
  });
}

void CFX_DIBitmap::TransferEqualFormatsOneBPP(
    int dest_left,
    int dest_top,
    int width,
    int height,
    RetainPtr<const CFX_DIBBase> source,
    int src_left,
    int src_top) {
  UNSAFE_TODO({
    for (int row = 0; row < height; ++row) {
      uint8_t* dest_scan = m_pBuffer.Get() + (dest_top + row) * GetPitch();
      const uint8_t* src_scan = source->GetScanline(src_top + row).data();
      for (int col = 0; col < width; ++col) {
        int src_idx = src_left + col;
        int dest_idx = dest_left + col;
        if (src_scan[(src_idx) / 8] & (1 << (7 - (src_idx) % 8))) {
          dest_scan[(dest_idx) / 8] |= 1 << (7 - (dest_idx) % 8);
        } else {
          dest_scan[(dest_idx) / 8] &= ~(1 << (7 - (dest_idx) % 8));
        }
      }
    }
  });
}

void CFX_DIBitmap::SetRedFromAlpha() {
  CHECK_EQ(FXDIB_Format::kArgb, GetFormat());
  CHECK(m_pBuffer);

  for (int row = 0; row < GetHeight(); row++) {
    auto scanline =
        GetWritableScanlineAs<FX_BGRA_STRUCT<uint8_t>>(row).first(GetWidth());
    for (auto& pixel : scanline) {
      pixel.red = pixel.alpha;
    }
  }
}

void CFX_DIBitmap::SetUniformOpaqueAlpha() {
  CHECK_EQ(FXDIB_Format::kArgb, GetFormat());
  CHECK(m_pBuffer);

  for (int row = 0; row < GetHeight(); row++) {
    auto scanline =
        GetWritableScanlineAs<FX_BGRA_STRUCT<uint8_t>>(row).first(GetWidth());
    for (auto& pixel : scanline) {
      pixel.alpha = 0xff;
    }
  }
}

bool CFX_DIBitmap::MultiplyAlphaMask(RetainPtr<const CFX_DIBitmap> mask) {
  CHECK_EQ(GetWidth(), mask->GetWidth());
  CHECK_EQ(GetHeight(), mask->GetHeight());
  CHECK_EQ(FXDIB_Format::k8bppMask, mask->GetFormat());
  CHECK(m_pBuffer);

  if (GetFormat() == FXDIB_Format::kRgb32) {
    if (!ConvertFormat(FXDIB_Format::kArgb)) {
      return false;
    }

    for (int row = 0; row < GetHeight(); row++) {
      auto dest_scan =
          GetWritableScanlineAs<FX_BGRA_STRUCT<uint8_t>>(row).first(GetWidth());
      auto mask_scan = mask->GetScanline(row).first(GetWidth());
      for (int col = 0; col < GetWidth(); col++) {
        // Since the `dest_scan` value always starts out as 255 in this case,
        // simplify 255 * x / 255.
        dest_scan[col].alpha = mask_scan[col];
      }
    }
    return true;
  }

  CHECK_EQ(GetFormat(), FXDIB_Format::kArgb);
  for (int row = 0; row < GetHeight(); row++) {
    auto dest_scan =
        GetWritableScanlineAs<FX_BGRA_STRUCT<uint8_t>>(row).first(GetWidth());
    auto mask_scan = mask->GetScanline(row).first(GetWidth());
    for (int col = 0; col < GetWidth(); col++) {
      dest_scan[col].alpha = dest_scan[col].alpha * mask_scan[col] / 255;
    }
  }
  return true;
}

bool CFX_DIBitmap::MultiplyAlpha(float alpha) {
  CHECK_GE(alpha, 0.0f);
  CHECK_LE(alpha, 1.0f);
  CHECK(!IsMaskFormat());

  if (alpha == 1.0f) {
    return true;
  }

  if (!m_pBuffer) {
    return false;
  }

  if (!ConvertFormat(FXDIB_Format::kArgb)) {
    return false;
  }

  const int bitmap_alpha = static_cast<int>(alpha * 255.0f);
  for (int row = 0; row < GetHeight(); row++) {
    auto dest_scan =
        GetWritableScanlineAs<FX_BGRA_STRUCT<uint8_t>>(row).first(GetWidth());
    for (auto& pixel : dest_scan) {
      pixel.alpha = pixel.alpha * bitmap_alpha / 255;
    }
  }
  return true;
}

#if defined(PDF_USE_SKIA)
uint32_t CFX_DIBitmap::GetPixelForTesting(int x, int y) const {
  if (!m_pBuffer)
    return 0;

  FX_SAFE_UINT32 offset = x;
  offset *= GetBPP();
  offset /= 8;
  if (!offset.IsValid())
    return 0;

  uint8_t* pos =
      UNSAFE_TODO(m_pBuffer.Get() + y * GetPitch() + offset.ValueOrDie());
  switch (GetFormat()) {
    case FXDIB_Format::kInvalid:
      return 0;
    case FXDIB_Format::k1bppMask: {
      if ((*pos) & (1 << (7 - x % 8))) {
        return 0xff000000;
      }
      return 0;
    }
    case FXDIB_Format::k1bppRgb: {
      if ((*pos) & (1 << (7 - x % 8))) {
        return HasPalette() ? GetPaletteSpan()[1] : 0xffffffff;
      }
      return HasPalette() ? GetPaletteSpan()[0] : 0xff000000;
    }
    case FXDIB_Format::k8bppMask:
      return (*pos) << 24;
    case FXDIB_Format::k8bppRgb:
      return HasPalette() ? GetPaletteSpan()[*pos]
                          : ArgbEncode(0xff, *pos, *pos, *pos);
    case FXDIB_Format::kRgb:
    case FXDIB_Format::kRgb32:
      return UNSAFE_TODO(FXARGB_GetDIB(pos) | 0xff000000);
    case FXDIB_Format::kArgb:
      return UNSAFE_TODO(FXARGB_GetDIB(pos));
  }
}
#endif  // defined(PDF_USE_SKIA)

void CFX_DIBitmap::ConvertBGRColorScale(uint32_t forecolor,
                                        uint32_t backcolor) {
  int fr = FXSYS_GetRValue(forecolor);
  int fg = FXSYS_GetGValue(forecolor);
  int fb = FXSYS_GetBValue(forecolor);
  int br = FXSYS_GetRValue(backcolor);
  int bg = FXSYS_GetGValue(backcolor);
  int bb = FXSYS_GetBValue(backcolor);
  if (GetBPP() <= 8) {
    if (forecolor == 0 && backcolor == 0xffffff && !HasPalette())
      return;

    BuildPalette();
    int size = 1 << GetBPP();
    for (int i = 0; i < size; ++i) {
      int gray = FXRGB2GRAY(FXARGB_R(m_palette[i]), FXARGB_G(m_palette[i]),
                            FXARGB_B(m_palette[i]));
      m_palette[i] =
          ArgbEncode(0xff, br + (fr - br) * gray / 255,
                     bg + (fg - bg) * gray / 255, bb + (fb - bb) * gray / 255);
    }
    return;
  }
  UNSAFE_TODO({
    if (forecolor == 0 && backcolor == 0xffffff) {
      for (int row = 0; row < GetHeight(); ++row) {
        uint8_t* scanline = m_pBuffer.Get() + row * GetPitch();
        int gap = GetBPP() / 8 - 2;
        for (int col = 0; col < GetWidth(); ++col) {
          int gray = FXRGB2GRAY(scanline[2], scanline[1], scanline[0]);
          *scanline++ = gray;
          *scanline++ = gray;
          *scanline = gray;
          scanline += gap;
        }
      }
      return;
    }
    for (int row = 0; row < GetHeight(); ++row) {
      uint8_t* scanline = m_pBuffer.Get() + row * GetPitch();
      int gap = GetBPP() / 8 - 2;
      for (int col = 0; col < GetWidth(); ++col) {
        int gray = FXRGB2GRAY(scanline[2], scanline[1], scanline[0]);
        *scanline++ = bb + (fb - bb) * gray / 255;
        *scanline++ = bg + (fg - bg) * gray / 255;
        *scanline = br + (fr - br) * gray / 255;
        scanline += gap;
      }
    }
  });
}

bool CFX_DIBitmap::ConvertColorScale(uint32_t forecolor, uint32_t backcolor) {
  if (!m_pBuffer || IsMaskFormat())
    return false;

  ConvertBGRColorScale(forecolor, backcolor);
  return true;
}

// static
std::optional<CFX_DIBitmap::PitchAndSize> CFX_DIBitmap::CalculatePitchAndSize(
    int width,
    int height,
    FXDIB_Format format,
    uint32_t pitch) {
  if (width <= 0 || height <= 0) {
    return std::nullopt;
  }
  int bpp = GetBppFromFormat(format);
  if (!bpp) {
    return std::nullopt;
  }
  if (pitch == 0) {
    std::optional<uint32_t> pitch32 = fxge::CalculatePitch32(bpp, width);
    if (!pitch32.has_value()) {
      return std::nullopt;
    }
    pitch = pitch32.value();
  } else {
    std::optional<uint32_t> actual_pitch =
        fxge::CalculatePitch8(bpp, /*components=*/1, width);
    if (!actual_pitch.has_value() || pitch < actual_pitch.value()) {
      return std::nullopt;
    }
  }
  FX_SAFE_UINT32 safe_size = pitch;
  safe_size *= height;
  if (!safe_size.IsValid())
    return std::nullopt;

  return PitchAndSize{pitch, safe_size.ValueOrDie()};
}

bool CFX_DIBitmap::CompositeBitmap(int dest_left,
                                   int dest_top,
                                   int width,
                                   int height,
                                   RetainPtr<const CFX_DIBBase> source,
                                   int src_left,
                                   int src_top,
                                   BlendMode blend_type,
                                   const CFX_ClipRgn* pClipRgn,
                                   bool bRgbByteOrder) {
  // Should have called CompositeMask().
  CHECK(!source->IsMaskFormat());

  if (!m_pBuffer)
    return false;

  if (GetBPP() < 8) {
    return false;
  }

  if (!GetOverlapRect(dest_left, dest_top, width, height, source->GetWidth(),
                      source->GetHeight(), src_left, src_top, pClipRgn)) {
    return true;
  }

  RetainPtr<CFX_DIBitmap> pClipMask;
  FX_RECT clip_box;
  if (pClipRgn && pClipRgn->GetType() != CFX_ClipRgn::kRectI) {
    pClipMask = pClipRgn->GetMask();
    clip_box = pClipRgn->GetBox();
  }
  CFX_ScanlineCompositor compositor;
  if (!compositor.Init(GetFormat(), source->GetFormat(),
                       source->GetPaletteSpan(), 0, blend_type,
                       pClipMask != nullptr, bRgbByteOrder)) {
    return false;
  }
  const int dest_Bpp = GetBPP() / 8;
  const int src_Bpp = source->GetBPP() / 8;
  const bool bRgb = src_Bpp > 1;
  if (!bRgb && !source->HasPalette()) {
    return false;
  }

  for (int row = 0; row < height; row++) {
    pdfium::span<uint8_t> dest_scan =
        GetWritableScanline(dest_top + row).subspan(dest_left * dest_Bpp);
    pdfium::span<const uint8_t> src_scan =
        source->GetScanline(src_top + row).subspan(src_left * src_Bpp);
    pdfium::span<const uint8_t> clip_scan;
    if (pClipMask) {
      clip_scan = pClipMask->GetWritableScanline(dest_top + row - clip_box.top)
                      .subspan(dest_left - clip_box.left);
    }
    if (bRgb) {
      compositor.CompositeRgbBitmapLine(dest_scan, src_scan, width, clip_scan);
    } else {
      compositor.CompositePalBitmapLine(dest_scan, src_scan, src_left, width,
                                        clip_scan);
    }
  }
  return true;
}

bool CFX_DIBitmap::CompositeMask(int dest_left,
                                 int dest_top,
                                 int width,
                                 int height,
                                 const RetainPtr<const CFX_DIBBase>& pMask,
                                 uint32_t color,
                                 int src_left,
                                 int src_top,
                                 BlendMode blend_type,
                                 const CFX_ClipRgn* pClipRgn,
                                 bool bRgbByteOrder) {
  // Should have called CompositeBitmap().
  CHECK(pMask->IsMaskFormat());

  if (!m_pBuffer)
    return false;

  if (GetBPP() < 8) {
    return false;
  }

  if (!GetOverlapRect(dest_left, dest_top, width, height, pMask->GetWidth(),
                      pMask->GetHeight(), src_left, src_top, pClipRgn)) {
    return true;
  }

  int src_alpha = FXARGB_A(color);
  if (src_alpha == 0)
    return true;

  RetainPtr<CFX_DIBitmap> pClipMask;
  FX_RECT clip_box;
  if (pClipRgn && pClipRgn->GetType() != CFX_ClipRgn::kRectI) {
    pClipMask = pClipRgn->GetMask();
    clip_box = pClipRgn->GetBox();
  }
  int src_bpp = pMask->GetBPP();
  int Bpp = GetBPP() / 8;
  CFX_ScanlineCompositor compositor;
  if (!compositor.Init(GetFormat(), pMask->GetFormat(), {}, color, blend_type,
                       pClipMask != nullptr, bRgbByteOrder)) {
    return false;
  }
  for (int row = 0; row < height; row++) {
    pdfium::span<uint8_t> dest_scan =
        GetWritableScanline(dest_top + row).subspan(dest_left * Bpp);
    pdfium::span<const uint8_t> src_scan = pMask->GetScanline(src_top + row);
    pdfium::span<const uint8_t> clip_scan;
    if (pClipMask) {
      clip_scan = pClipMask->GetScanline(dest_top + row - clip_box.top)
                      .subspan(dest_left - clip_box.left);
    }
    if (src_bpp == 1) {
      compositor.CompositeBitMaskLine(dest_scan, src_scan, src_left, width,
                                      clip_scan);
    } else {
      compositor.CompositeByteMaskLine(dest_scan, src_scan.subspan(src_left),
                                       width, clip_scan);
    }
  }
  return true;
}

void CFX_DIBitmap::CompositeOneBPPMask(int dest_left,
                                       int dest_top,
                                       int width,
                                       int height,
                                       RetainPtr<const CFX_DIBBase> source,
                                       int src_left,
                                       int src_top) {
  if (GetBPP() != 1) {
    return;
  }
  if (!GetOverlapRect(dest_left, dest_top, width, height, source->GetWidth(),
                      source->GetHeight(), src_left, src_top, nullptr)) {
    return;
  }
  UNSAFE_TODO({
    for (int row = 0; row < height; ++row) {
      uint8_t* dest_scan = m_pBuffer.Get() + (dest_top + row) * GetPitch();
      const uint8_t* src_scan = source->GetScanline(src_top + row).data();
      for (int col = 0; col < width; ++col) {
        int src_idx = src_left + col;
        int dest_idx = dest_left + col;
        if (src_scan[src_idx / 8] & (1 << (7 - src_idx % 8))) {
          dest_scan[dest_idx / 8] |= 1 << (7 - dest_idx % 8);
        }
      }
    }
  });
}

bool CFX_DIBitmap::CompositeRect(int left,
                                 int top,
                                 int width,
                                 int height,
                                 uint32_t color) {
  if (!m_pBuffer)
    return false;

  int src_alpha = FXARGB_A(color);
  if (src_alpha == 0)
    return true;

  FX_RECT rect(left, top, left + width, top + height);
  rect.Intersect(0, 0, GetWidth(), GetHeight());
  if (rect.IsEmpty())
    return true;

  width = rect.Width();
  uint32_t dst_color = color;
  uint8_t* color_p = reinterpret_cast<uint8_t*>(&dst_color);
  UNSAFE_TODO({
    if (GetBPP() == 8) {
      uint8_t gray =
          IsMaskFormat()
              ? 255
              : (uint8_t)FXRGB2GRAY((int)color_p[2], color_p[1], color_p[0]);
      for (int row = rect.top; row < rect.bottom; row++) {
        uint8_t* dest_scan = m_pBuffer.Get() + row * GetPitch() + rect.left;
        if (src_alpha == 255) {
          FXSYS_memset(dest_scan, gray, width);
        } else {
          for (int col = 0; col < width; col++) {
            *dest_scan = FXDIB_ALPHA_MERGE(*dest_scan, gray, src_alpha);
            dest_scan++;
          }
        }
      }
      return true;
    }
    if (GetBPP() == 1) {
      int left_shift = rect.left % 8;
      int right_shift = rect.right % 8;
      int new_width = rect.right / 8 - rect.left / 8;
      int index = 0;
      if (HasPalette()) {
        for (int i = 0; i < 2; i++) {
          if (GetPaletteSpan()[i] == color) {
            index = i;
          }
        }
      } else {
        index = (static_cast<uint8_t>(color) == 0xff) ? 1 : 0;
      }
      for (int row = rect.top; row < rect.bottom; row++) {
        uint8_t* dest_scan_top =
            GetWritableScanline(row).subspan(rect.left / 8).data();
        uint8_t* dest_scan_top_r =
            GetWritableScanline(row).subspan(rect.right / 8).data();
        uint8_t left_flag = *dest_scan_top & (255 << (8 - left_shift));
        uint8_t right_flag = *dest_scan_top_r & (255 >> right_shift);
        if (new_width) {
          FXSYS_memset(dest_scan_top + 1, index ? 255 : 0, new_width - 1);
          if (!index) {
            *dest_scan_top &= left_flag;
            *dest_scan_top_r &= right_flag;
          } else {
            *dest_scan_top |= ~left_flag;
            *dest_scan_top_r |= ~right_flag;
          }
        } else {
          if (!index) {
            *dest_scan_top &= left_flag | right_flag;
          } else {
            *dest_scan_top |= ~(left_flag | right_flag);
          }
        }
      }
      return true;
    }

    CHECK_GE(GetBPP(), 24);
    color_p[3] = static_cast<uint8_t>(src_alpha);
    int Bpp = GetBPP() / 8;
    const bool bAlpha = IsAlphaFormat();
    if (bAlpha) {
      // Other formats with alpha have already been handled above.
      DCHECK_EQ(GetFormat(), FXDIB_Format::kArgb);
    }
    if (src_alpha == 255) {
      for (int row = rect.top; row < rect.bottom; row++) {
        uint8_t* dest_scan =
            m_pBuffer.Get() + row * GetPitch() + rect.left * Bpp;
        if (Bpp == 4) {
          uint32_t* scan = reinterpret_cast<uint32_t*>(dest_scan);
          for (int col = 0; col < width; col++) {
            *scan++ = dst_color;
          }
        } else {
          for (int col = 0; col < width; col++) {
            *dest_scan++ = color_p[0];
            *dest_scan++ = color_p[1];
            *dest_scan++ = color_p[2];
          }
        }
      }
      return true;
    }
    for (int row = rect.top; row < rect.bottom; row++) {
      uint8_t* dest_scan = m_pBuffer.Get() + row * GetPitch() + rect.left * Bpp;
      if (bAlpha) {
        for (int col = 0; col < width; col++) {
          uint8_t back_alpha = dest_scan[3];
          if (back_alpha == 0) {
            FXARGB_SetDIB(dest_scan, ArgbEncode(src_alpha, color_p[2],
                                                color_p[1], color_p[0]));
            dest_scan += 4;
            continue;
          }
          uint8_t dest_alpha =
              back_alpha + src_alpha - back_alpha * src_alpha / 255;
          int alpha_ratio = src_alpha * 255 / dest_alpha;
          *dest_scan = FXDIB_ALPHA_MERGE(*dest_scan, color_p[0], alpha_ratio);
          dest_scan++;
          *dest_scan = FXDIB_ALPHA_MERGE(*dest_scan, color_p[1], alpha_ratio);
          dest_scan++;
          *dest_scan = FXDIB_ALPHA_MERGE(*dest_scan, color_p[2], alpha_ratio);
          dest_scan++;
          *dest_scan++ = dest_alpha;
        }
      } else {
        for (int col = 0; col < width; col++) {
          for (int comps = 0; comps < Bpp; comps++) {
            if (comps == 3) {
              *dest_scan++ = 255;
              continue;
            }
            *dest_scan =
                FXDIB_ALPHA_MERGE(*dest_scan, color_p[comps], src_alpha);
            dest_scan++;
          }
        }
      }
    }
  });
  return true;
}

bool CFX_DIBitmap::ConvertFormat(FXDIB_Format dest_format) {
  DCHECK(dest_format == FXDIB_Format::k8bppMask ||
         dest_format == FXDIB_Format::kArgb ||
         dest_format == FXDIB_Format::kRgb32 ||
         dest_format == FXDIB_Format::kRgb);

  if (dest_format == GetFormat()) {
    return true;
  }

  if (dest_format == FXDIB_Format::k8bppMask &&
      GetFormat() == FXDIB_Format::k8bppRgb && !HasPalette()) {
    SetFormat(FXDIB_Format::k8bppMask);
    return true;
  }
  if (dest_format == FXDIB_Format::kArgb &&
      GetFormat() == FXDIB_Format::kRgb32) {
    SetFormat(FXDIB_Format::kArgb);
    UNSAFE_TODO({
      for (int row = 0; row < GetHeight(); row++) {
        uint8_t* scanline = m_pBuffer.Get() + row * GetPitch() + 3;
        for (int col = 0; col < GetWidth(); col++) {
          *scanline = 0xff;
          scanline += 4;
        }
      }
    });
    return true;
  }
  int dest_bpp = GetBppFromFormat(dest_format);
  int dest_pitch = fxge::CalculatePitch32OrDie(dest_bpp, GetWidth());
  const size_t dest_buf_size = dest_pitch * GetHeight() + 4;
  std::unique_ptr<uint8_t, FxFreeDeleter> dest_buf(
      FX_TryAlloc(uint8_t, dest_buf_size));
  if (!dest_buf)
    return false;

  if (dest_format == FXDIB_Format::kArgb) {
    UNSAFE_TODO(FXSYS_memset(dest_buf.get(), 0xff, dest_buf_size));
  }
  RetainPtr<CFX_DIBBase> holder(this);
  // SAFETY: `dest_buf` allocated with `dest_buf_size` bytes above.
  m_palette = ConvertBuffer(
      dest_format,
      UNSAFE_BUFFERS(pdfium::make_span(dest_buf.get(), dest_buf_size)),
      dest_pitch, GetWidth(), GetHeight(), holder, /*src_left=*/0,
      /*src_top=*/0);
  m_pBuffer = std::move(dest_buf);
  SetFormat(dest_format);
  SetPitch(dest_pitch);
  return true;
}