diff --git a/core/fpdfapi/page/cpdf_page.cpp b/core/fpdfapi/page/cpdf_page.cpp
index dfbd342..6213e5f 100644
--- a/core/fpdfapi/page/cpdf_page.cpp
+++ b/core/fpdfapi/page/cpdf_page.cpp
@@ -178,6 +178,35 @@
   return matrix;
 }
 
+// This method follows the same apparent logic as GetDisplayMatrix(). For
+// example, consider point 0. First, take the top left coordinate of the
+// rectangle in the transformed space. Now, calculate what this point was in the
+// original space by inverting. Note that this is not necessarily the same as
+// the top left corner of the original rectangle.
+CFX_Matrix CPDF_Page::GetDisplayMatrixWithTransformation(
+    int xPos,
+    int yPos,
+    int xSize,
+    int ySize,
+    const CFX_Matrix& transformation) {
+  CFX_FloatRect rect(xPos, yPos, xPos + xSize, yPos + ySize);
+  rect = transformation.TransformRect(rect);
+  CFX_Matrix inverse = transformation.GetInverse();
+  CFX_PointF point0(rect.left, rect.top);
+  CFX_PointF point1(rect.left, rect.bottom);
+  CFX_PointF point2(rect.right, rect.top);
+  point0 = inverse.Transform(point0);
+  point1 = inverse.Transform(point1);
+  point2 = inverse.Transform(point2);
+
+  CFX_Matrix matrix = m_PageMatrix;
+  matrix.Concat(CFX_Matrix(
+      (point2.x - point0.x) / m_PageWidth, (point2.y - point0.y) / m_PageWidth,
+      (point1.x - point0.x) / m_PageHeight,
+      (point1.y - point0.y) / m_PageHeight, point0.x, point0.y));
+  return matrix;
+}
+
 int CPDF_Page::GetPageRotation() const {
   CPDF_Object* pRotate = GetPageAttr("Rotate");
   int rotate = pRotate ? (pRotate->GetInteger() / 90) % 4 : 0;
diff --git a/core/fpdfapi/page/cpdf_page.h b/core/fpdfapi/page/cpdf_page.h
index 1891e65..47fba3c 100644
--- a/core/fpdfapi/page/cpdf_page.h
+++ b/core/fpdfapi/page/cpdf_page.h
@@ -38,11 +38,16 @@
                               int xSize,
                               int ySize,
                               int iRotate) const;
+  CFX_Matrix GetDisplayMatrixWithTransformation(
+      int xPos,
+      int yPos,
+      int xSize,
+      int ySize,
+      const CFX_Matrix& transformation);
 
   float GetPageWidth() const { return m_PageWidth; }
   float GetPageHeight() const { return m_PageHeight; }
   CFX_FloatRect GetPageBBox() const { return m_BBox; }
-  const CFX_Matrix& GetPageMatrix() const { return m_PageMatrix; }
   int GetPageRotation() const;
   CPDF_PageRenderCache* GetRenderCache() const { return m_pPageRender.get(); }
 
diff --git a/fpdfsdk/fpdfview.cpp b/fpdfsdk/fpdfview.cpp
index e93e8bc..5bcc643 100644
--- a/fpdfsdk/fpdfview.cpp
+++ b/fpdfsdk/fpdfview.cpp
@@ -1004,15 +1004,13 @@
     clipping_rect.top = clipping->top;
   }
   FX_RECT clip_rect = clipping_rect.ToFxRect();
-
-  CFX_Matrix transform_matrix = pPage->GetDisplayMatrix(
-      clip_rect.left, clip_rect.top, clip_rect.Width(), clip_rect.Height(), 0);
-  if (matrix) {
-    transform_matrix.Concat(CFX_Matrix(matrix->a, matrix->b, matrix->c,
-                                       matrix->d, matrix->e, matrix->f));
-  }
-  RenderPageImpl(pContext, pPage, transform_matrix, clip_rect, flags, true,
-                 nullptr);
+  RenderPageImpl(
+      pContext, pPage,
+      pPage->GetDisplayMatrixWithTransformation(
+          clip_rect.left, clip_rect.top, clip_rect.Width(), clip_rect.Height(),
+          CFX_Matrix(matrix->a, matrix->b, matrix->c, matrix->d, matrix->e,
+                     matrix->f)),
+      clip_rect, flags, true, nullptr);
 
   pPage->SetRenderContext(nullptr);
 }
diff --git a/fpdfsdk/fpdfview_embeddertest.cpp b/fpdfsdk/fpdfview_embeddertest.cpp
index 8576104..97ba9d7 100644
--- a/fpdfsdk/fpdfview_embeddertest.cpp
+++ b/fpdfsdk/fpdfview_embeddertest.cpp
@@ -5,6 +5,7 @@
 #include <limits>
 #include <string>
 
+#include "core/fxcrt/fx_coordinates.h"
 #include "fpdfsdk/fpdfview_c_api_test.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
@@ -350,75 +351,119 @@
 }
 
 TEST_F(FPDFViewEmbeddertest, FPDF_RenderPageBitmapWithMatrix) {
-  const char kOriginalMD5[] = "210157942bcce97b057a1107a1fd62f8";
-  const char kTopLeftQuarterMD5[] = "c54d58dda13e3cd04eb63e1d0db0feda";
-  const char kTrimmedMD5[] = "88225d7951a21d0eef191cfed06c36ce";
-  const char kRotatedMD5[] = "7d38bc58aa50ad271bc432e77256d3de";
+  const char* const kRotatedMD5[4] = {
+      "0a90de37f52127619c3dfb642b5fa2fe", "d599429574ff0dcad3bc898ea8b874ca",
+      "0113386bb0bd45125bacc6dee78bfe78", "051fcfa4c1f9de28765705633a8ef3a9"};
+  const char kTopLeftQuarterMD5[] = "4982be08db3f6d2e6409186ebbced9eb";
+  const char kHoriStretchedMD5[] = "004bf38f3c5c76a644e6fca204747f21";
+  const char kRotateandStretchMD5[] = "0ea95cacc716d003cf063a2c5ed6c8d7";
 
   EXPECT_TRUE(OpenDocument("rectangles.pdf"));
   FPDF_PAGE page = LoadPage(0);
   EXPECT_NE(nullptr, page);
-  const int width = static_cast<int>(FPDF_GetPageWidth(page));
-  const int height = static_cast<int>(FPDF_GetPageHeight(page));
-  EXPECT_EQ(200, width);
-  EXPECT_EQ(200, height);
+  const int initial_width = static_cast<int>(FPDF_GetPageWidth(page));
+  const int initial_height = static_cast<int>(FPDF_GetPageHeight(page));
+  EXPECT_EQ(200, initial_width);
+  EXPECT_EQ(300, initial_height);
 
   FPDF_BITMAP bitmap = RenderPage(page);
-  CompareBitmap(bitmap, width, height, kOriginalMD5);
+  CompareBitmap(bitmap, initial_width, initial_height, kRotatedMD5[0]);
   FPDFBitmap_Destroy(bitmap);
 
-  // Try rendering with an identity matrix. The output should be the same as
-  // the RenderPage() output.
-  FS_MATRIX matrix;
-  matrix.a = 1;
-  matrix.b = 0;
-  matrix.c = 0;
-  matrix.d = 1;
-  matrix.e = 0;
-  matrix.f = 0;
-
+  int width;
+  int height;
   FS_RECTF rect;
   rect.left = 0;
   rect.top = 0;
-  rect.right = width;
-  rect.bottom = height;
+  FS_MATRIX matrix;
 
-  bitmap = FPDFBitmap_Create(width, height, 0);
-  FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
-  FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
-  CompareBitmap(bitmap, width, height, kOriginalMD5);
-  FPDFBitmap_Destroy(bitmap);
+  // Try the easy rotations: 0, 90, 180, 270 clockwise. The output should be the
+  // same as FPDF_RenderPageBitmap with the appropriate rotation flag. Per PDF
+  // spec section 4.2.2, a t degree rotation is represented by [cos(t) sin(t)
+  // -sin(t) cos(t) 0 0] (matrix goes on the right in the multiplication).
+  rect.right = initial_width;
+  rect.bottom = initial_height;
+  CFX_Matrix rot_matrices[4] = {
+      CFX_Matrix(1, 0, 0, 1, 0, 0), CFX_Matrix(0, -1, 1, 0, 0, 0),
+      CFX_Matrix(-1, 0, 0, -1, 0, 0), CFX_Matrix(0, 1, -1, 0, 0, 0)};
+  for (int rot = 0; rot < 4; ++rot) {
+    matrix.a = rot_matrices[rot].a;
+    matrix.b = rot_matrices[rot].b;
+    matrix.c = rot_matrices[rot].c;
+    matrix.d = rot_matrices[rot].d;
+    matrix.e = rot_matrices[rot].e;
+    matrix.f = rot_matrices[rot].f;
+    if (rot % 2 == 0) {
+      width = initial_width;
+      height = initial_height;
+    } else {
+      width = initial_height;
+      height = initial_width;
+    }
+    rect.right = width;
+    rect.bottom = height;
+
+    bitmap = FPDFBitmap_Create(width, height, 0);
+    FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
+    FPDF_RenderPageBitmap(bitmap, page, 0, 0, width, height, rot, 0);
+    CompareBitmap(bitmap, width, height, kRotatedMD5[rot]);
+    FPDFBitmap_Destroy(bitmap);
+
+    bitmap = FPDFBitmap_Create(width, height, 0);
+    FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
+    FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
+    CompareBitmap(bitmap, width, height, kRotatedMD5[rot]);
+    FPDFBitmap_Destroy(bitmap);
+  }
+  // TODO(npm): what to do with transformations that do not align the page with
+  // the axis, like a 45 degree rotation (currently, part of the page gets cut
+  // out). pdfium:849
 
   // Now render again with the image scaled smaller.
+  width = initial_width / 2;
+  height = initial_height / 2;
   matrix.a = 0.5;
+  matrix.b = 0;
+  matrix.c = 0;
   matrix.d = 0.5;
 
+  rect.right = width;
+  rect.bottom = height;
+
   bitmap = FPDFBitmap_Create(width, height, 0);
   FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
   FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
   CompareBitmap(bitmap, width, height, kTopLeftQuarterMD5);
   FPDFBitmap_Destroy(bitmap);
 
-  // Now render again with the image scaled larger horizontally (will be
-  // trimmed).
+  // Now render again with the image scaled larger horizontally.
+  width = initial_width * 2;
+  height = initial_height;
   matrix.a = 2;
   matrix.d = 1;
+  rect.right = width;
+  rect.bottom = height;
   bitmap = FPDFBitmap_Create(width, height, 0);
   FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
   FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
-  CompareBitmap(bitmap, width, height, kTrimmedMD5);
+  CompareBitmap(bitmap, width, height, kHoriStretchedMD5);
   FPDFBitmap_Destroy(bitmap);
 
-  // Now try a 90 degree rotation
+  // Test a rotation followed by a stretch.
+  width = initial_height * 2;
+  height = initial_width;
   matrix.a = 0;
-  matrix.b = 1;
-  matrix.c = -1;
+  matrix.b = -1;
+  matrix.c = 2;
   matrix.d = 0;
-  matrix.e = width;
+  matrix.e = 0;
+  matrix.f = 0;
+  rect.right = width;
+  rect.bottom = height;
   bitmap = FPDFBitmap_Create(width, height, 0);
   FPDFBitmap_FillRect(bitmap, 0, 0, width, height, 0xFFFFFFFF);
   FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
-  CompareBitmap(bitmap, width, height, kRotatedMD5);
+  CompareBitmap(bitmap, width, height, kRotateandStretchMD5);
   FPDFBitmap_Destroy(bitmap);
 
   UnloadPage(page);
diff --git a/public/fpdfview.h b/public/fpdfview.h
index c74fcb9..135d00a 100644
--- a/public/fpdfview.h
+++ b/public/fpdfview.h
@@ -666,7 +666,7 @@
 //                          by FPDFBitmap_Create or retrieved by
 //                          FPDFImageObj_GetBitmap.
 //          page        -   Handle to the page. Returned by FPDF_LoadPage
-//          matrix      -   The transform matrix.
+//          matrix      -   The transform matrix. It must be invertible.
 //          clipping    -   The rect to clip to.
 //          flags       -   0 for normal display, or combination of the Page
 //                          Rendering flags defined above. With the FPDF_ANNOT
@@ -674,7 +674,7 @@
 //                          user-interaction, which are all annotations except
 //                          widget and popup annotations.
 // Return value:
-//          None.
+//          None. Note that behavior is undefined if det of |matrix| is 0.
 FPDF_EXPORT void FPDF_CALLCONV
 FPDF_RenderPageBitmapWithMatrix(FPDF_BITMAP bitmap,
                                 FPDF_PAGE page,
diff --git a/testing/resources/rectangles.in b/testing/resources/rectangles.in
index ed71cf8..49932ff 100644
--- a/testing/resources/rectangles.in
+++ b/testing/resources/rectangles.in
@@ -6,7 +6,7 @@
 endobj
 {{object 2 0}} <<
   /Type /Pages
-  /MediaBox [ 0 0 200 200 ]
+  /MediaBox [ 0 0 200 300 ]
   /Count 1
   /Kids [ 3 0 R ]
 >>
@@ -22,13 +22,17 @@
 stream
 q
 0 0 0 rg
-10 80 50 30 re B*
+0 290 10 10 re B*
+10 150 50 30 re B*
 0 0 1 rg
-70 135 50 30 re B*
+190 290 10 10 re B*
+70 232 50 30 re B*
 0 1 0 rg
-130 80 50 30 re B*
+190 0 10 10 re B*
+130 150 50 30 re B*
 1 0 0 rg
-70 25 50 30 re B*
+0 0 10 10 re B*
+70 67 50 30 re B*
 Q
 endstream
 endobj
diff --git a/testing/resources/rectangles.pdf b/testing/resources/rectangles.pdf
index 718bee5..7bad251 100644
--- a/testing/resources/rectangles.pdf
+++ b/testing/resources/rectangles.pdf
@@ -7,7 +7,7 @@
 endobj
 2 0 obj <<
   /Type /Pages
-  /MediaBox [ 0 0 200 200 ]
+  /MediaBox [ 0 0 200 300 ]
   /Count 1
   /Kids [ 3 0 R ]
 >>
@@ -23,13 +23,17 @@
 stream
 q
 0 0 0 rg
-10 80 50 30 re B*
+0 290 10 10 re B*
+10 150 50 30 re B*
 0 0 1 rg
-70 135 50 30 re B*
+190 290 10 10 re B*
+70 232 50 30 re B*
 0 1 0 rg
-130 80 50 30 re B*
+190 0 10 10 re B*
+130 150 50 30 re B*
 1 0 0 rg
-70 25 50 30 re B*
+0 0 10 10 re B*
+70 67 50 30 re B*
 Q
 endstream
 endobj
@@ -42,5 +46,5 @@
 0000000230 00000 n 
 trailer<< /Root 1 0 R /Size 5 >>
 startxref
-382
+456
 %%EOF