Fix behavior of FPDF_RenderPageBitmapWithMatrix

This functional part of this CL is mostly a revert of
"Change behaviour of FPDF_RenderPageBitmapWithMatrix"
24b0733a72bbc4013bff8628f198b0aea807aa06

Besides the revert, the parameters passed to
pPage->GetDisplayMatrix() are changed to fix a bug with the previous
implementation: the page was scaled to fit inside the clipping_rect,
instead of clipped.

Bug: pdfium:849
Change-Id: I95d0a303a979c998026a3bd6963c8684a1209f03
Reviewed-on: https://pdfium-review.googlesource.com/22931
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

4 files changed, 179 insertions, 139 deletions

diff --git a/core/fpdfapi/page/cpdf_page.cpp b/core/fpdfapi/page/cpdf_page.cpp
index c6f4fb2a39..ee7b5d408a 100644
--- a/core/fpdfapi/page/cpdf_page.cpp
+++ b/core/fpdfapi/page/cpdf_page.cpp
@@ -177,35 +177,6 @@ CFX_Matrix CPDF_Page::GetDisplayMatrix(int xPos,
   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 e32a7f0fe8..e1b5bcfa44 100644
--- a/core/fpdfapi/page/cpdf_page.h
+++ b/core/fpdfapi/page/cpdf_page.h
@@ -38,12 +38,6 @@ class CPDF_Page : public CPDF_PageObjectHolder {
                               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; }
diff --git a/fpdfsdk/fpdfview.cpp b/fpdfsdk/fpdfview.cpp
index cec44a48f9..97fc02a234 100644
--- a/fpdfsdk/fpdfview.cpp
+++ b/fpdfsdk/fpdfview.cpp
@@ -1034,13 +1034,16 @@ FPDF_RenderPageBitmapWithMatrix(FPDF_BITMAP bitmap,
   if (clipping)
     clipping_rect = CFXFloatRectFromFSRECTF(*clipping);
   FX_RECT clip_rect = clipping_rect.ToFxRect();
-  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);
+
+  CFX_Matrix transform_matrix = pPage->GetDisplayMatrix(
+      0, 0, pPage->GetPageWidth(), pPage->GetPageHeight(), 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);
 
   pPage->SetRenderContext(nullptr);
 }
diff --git a/fpdfsdk/fpdfview_embeddertest.cpp b/fpdfsdk/fpdfview_embeddertest.cpp
index 7e93574059..cca77c9031 100644
--- a/fpdfsdk/fpdfview_embeddertest.cpp
+++ b/fpdfsdk/fpdfview_embeddertest.cpp
@@ -2,10 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <cmath>
 #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"
@@ -33,7 +33,15 @@ TEST(fpdf, CApiTest) {
   EXPECT_TRUE(CheckPDFiumCApi());
 }
 
-class FPDFViewEmbeddertest : public EmbedderTest {};
+class FPDFViewEmbeddertest : public EmbedderTest {
+ protected:
+  void TestRenderPageBitmapWithMatrix(FPDF_PAGE page,
+                                      const int bitmap_width,
+                                      const int bitmap_height,
+                                      const FS_MATRIX& matrix,
+                                      const FS_RECTF& rect,
+                                      const char* expected_md5);
+};
 
 TEST_F(FPDFViewEmbeddertest, Document) {
   EXPECT_TRUE(OpenDocument("about_blank.pdf"));
@@ -377,113 +385,177 @@ TEST_F(FPDFViewEmbeddertest, Hang_360) {
   EXPECT_FALSE(OpenDocument("bug_360.pdf"));
 }
 
+void FPDFViewEmbeddertest::TestRenderPageBitmapWithMatrix(
+    FPDF_PAGE page,
+    const int bitmap_width,
+    const int bitmap_height,
+    const FS_MATRIX& matrix,
+    const FS_RECTF& rect,
+    const char* expected_md5) {
+  FPDF_BITMAP bitmap = FPDFBitmap_Create(bitmap_width, bitmap_height, 0);
+  FPDFBitmap_FillRect(bitmap, 0, 0, bitmap_width, bitmap_height, 0xFFFFFFFF);
+  FPDF_RenderPageBitmapWithMatrix(bitmap, page, &matrix, &rect, 0);
+  CompareBitmap(bitmap, bitmap_width, bitmap_height, expected_md5);
+  FPDFBitmap_Destroy(bitmap);
+}
+
 TEST_F(FPDFViewEmbeddertest, FPDF_RenderPageBitmapWithMatrix) {
-  const char* const kRotatedMD5[4] = {
-      "0a90de37f52127619c3dfb642b5fa2fe", "d599429574ff0dcad3bc898ea8b874ca",
-      "0113386bb0bd45125bacc6dee78bfe78", "051fcfa4c1f9de28765705633a8ef3a9"};
-  const char kTopLeftQuarterMD5[] = "4982be08db3f6d2e6409186ebbced9eb";
-  const char kHoriStretchedMD5[] = "004bf38f3c5c76a644e6fca204747f21";
-  const char kRotateandStretchMD5[] = "0ea95cacc716d003cf063a2c5ed6c8d7";
+  const char kOriginalMD5[] = "0a90de37f52127619c3dfb642b5fa2fe";
+  const char kClippedMD5[] = "a84cab93c102b9b9290fba3047ba702c";
+  const char kTopLeftQuarterMD5[] = "f11a11137c8834389e31cf555a4a6979";
+  const char kHoriStretchedMD5[] = "48ef9205941ed19691ccfa00d717187e";
+  const char kRotated90ClockwiseMD5[] = "d8da2c7bf77521550d0f2752b9cf3482";
+  const char kRotated180ClockwiseMD5[] = "0113386bb0bd45125bacc6dee78bfe78";
+  const char kRotated270ClockwiseMD5[] = "a287e0f74ce203699cda89f9cc97a240";
+  const char kMirrorHoriMD5[] = "6e8d7a6fde39d8e720fb9e620102918c";
+  const char kMirrorVertMD5[] = "8f3a555ef9c0d5031831ae3715273707";
+  const char kLargerTopLeftQuarterMD5[] = "172a2f4adafbadbe98017b1c025b9e27";
+  const char kLargerMD5[] = "c806145641c3e6fc4e022c7065343749";
+  const char kLargerClippedMD5[] = "091d3b1c7933c8f6945eb2cb41e588e9";
+  const char kLargerRotatedMD5[] = "115f13353ebfc82ddb392d1f0059eb12";
+  const char kLargerRotatedLandscapeMD5[] = "c901239d17d84ac84cb6f2124da71b0d";
+  const char kLargerRotatedDiagonalMD5[] = "3d62417468bdaff0eb14391a0c30a3b1";
+  const char kTileMD5[] = "0a190003c97220bf8877684c8d7e89cf";
 
   EXPECT_TRUE(OpenDocument("rectangles.pdf"));
   FPDF_PAGE page = LoadPage(0);
   EXPECT_NE(nullptr, page);
-  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);
+  const int page_width = static_cast<int>(FPDF_GetPageWidth(page));
+  const int page_height = static_cast<int>(FPDF_GetPageHeight(page));
+  EXPECT_EQ(200, page_width);
+  EXPECT_EQ(300, page_height);
 
   FPDF_BITMAP bitmap = RenderPage(page);
-  CompareBitmap(bitmap, initial_width, initial_height, kRotatedMD5[0]);
+  CompareBitmap(bitmap, page_width, page_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).
-  FS_RECTF rect = {0, 0, initial_width, 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) {
-    int width;
-    int height;
-    FS_MATRIX matrix;
-    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.
-  int width = initial_width / 2;
-  int height = initial_height / 2;
-  FS_MATRIX matrix = {0.5, 0, 0, 0.5, 0, 0};
-
-  rect.right = width;
-  rect.bottom = height;
+  FS_RECTF page_rect{0, 0, page_width, page_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);
+  // Try rendering with an identity matrix. The output should be the same as
+  // the RenderPage() output.
+  FS_MATRIX identity_matrix{1, 0, 0, 1, 0, 0};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height, identity_matrix,
+                                 page_rect, kOriginalMD5);
 
-  // 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, kHoriStretchedMD5);
-  FPDFBitmap_Destroy(bitmap);
+  // Again render with an identity matrix but with a smaller clipping rect.
+  FS_RECTF middle_of_page_rect{page_width / 4, page_height / 4,
+                               page_width * 3 / 4, page_height * 3 / 4};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height, identity_matrix,
+                                 middle_of_page_rect, kClippedMD5);
 
-  // Test a rotation followed by a stretch.
-  width = initial_height * 2;
-  height = initial_width;
-  matrix.a = 0;
-  matrix.b = -1;
-  matrix.c = 2;
-  matrix.d = 0;
-  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, kRotateandStretchMD5);
-  FPDFBitmap_Destroy(bitmap);
+  // Now render again with the image scaled smaller.
+  FS_MATRIX half_scale_matrix{0.5, 0, 0, 0.5, 0, 0};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 half_scale_matrix, page_rect,
+                                 kTopLeftQuarterMD5);
+
+  // Now render again with the image scaled larger horizontally (the right half
+  // will be clipped).
+  FS_MATRIX stretch_x_matrix{2, 0, 0, 1, 0, 0};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 stretch_x_matrix, page_rect,
+                                 kHoriStretchedMD5);
+
+  // Try a 90 degree rotation clockwise but with the same bitmap size, so part
+  // will be clipped.
+  FS_MATRIX rotate_90_matrix{0, 1, -1, 0, page_width, 0};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 rotate_90_matrix, page_rect,
+                                 kRotated90ClockwiseMD5);
+
+  // 180 degree rotation clockwise.
+  FS_MATRIX rotate_180_matrix{-1, 0, 0, -1, page_width, page_height};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 rotate_180_matrix, page_rect,
+                                 kRotated180ClockwiseMD5);
+
+  // 270 degree rotation clockwise.
+  FS_MATRIX rotate_270_matrix{0, -1, 1, 0, 0, page_width};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 rotate_270_matrix, page_rect,
+                                 kRotated270ClockwiseMD5);
+
+  // Mirror horizontally.
+  FS_MATRIX mirror_hori_matrix{-1, 0, 0, 1, page_width, 0};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 mirror_hori_matrix, page_rect, kMirrorHoriMD5);
+
+  // Mirror vertically.
+  FS_MATRIX mirror_vert_matrix{1, 0, 0, -1, 0, page_height};
+  TestRenderPageBitmapWithMatrix(page, page_width, page_height,
+                                 mirror_vert_matrix, page_rect, kMirrorVertMD5);
+
+  // Tests rendering to a larger bitmap
+  const int bitmap_width = page_width * 2;
+  const int bitmap_height = page_height * 2;
+
+  // Render using an identity matrix and the whole bitmap area as clipping rect.
+  FS_RECTF bitmap_rect{0, 0, bitmap_width, bitmap_height};
+  TestRenderPageBitmapWithMatrix(page, bitmap_width, bitmap_height,
+                                 identity_matrix, bitmap_rect,
+                                 kLargerTopLeftQuarterMD5);
+
+  // Render using a scaling matrix to fill the larger bitmap.
+  FS_MATRIX double_scale_matrix{2, 0, 0, 2, 0, 0};
+  TestRenderPageBitmapWithMatrix(page, bitmap_width, bitmap_height,
+                                 double_scale_matrix, bitmap_rect, kLargerMD5);
+
+  // Render the larger image again but with clipping.
+  FS_RECTF middle_of_bitmap_rect{bitmap_width / 4, bitmap_height / 4,
+                                 bitmap_width * 3 / 4, bitmap_height * 3 / 4};
+  TestRenderPageBitmapWithMatrix(page, bitmap_width, bitmap_height,
+                                 double_scale_matrix, middle_of_bitmap_rect,
+                                 kLargerClippedMD5);
+
+  // On the larger bitmap, try a 90 degree rotation but with the same bitmap
+  // size, so part will be clipped.
+  FS_MATRIX rotate_90_scale_2_matrix{0, 2, -2, 0, bitmap_width, 0};
+  TestRenderPageBitmapWithMatrix(page, bitmap_width, bitmap_height,
+                                 rotate_90_scale_2_matrix, bitmap_rect,
+                                 kLargerRotatedMD5);
+
+  // On the larger bitmap, apply 90 degree rotation to a bitmap with the
+  // appropriate dimensions.
+  const int landscape_bitmap_width = bitmap_height;
+  const int landscape_bitmap_height = bitmap_width;
+  FS_RECTF landscape_bitmap_rect{0, 0, landscape_bitmap_width,
+                                 landscape_bitmap_height};
+  FS_MATRIX landscape_rotate_90_scale_2_matrix{
+      0, 2, -2, 0, landscape_bitmap_width, 0};
+  TestRenderPageBitmapWithMatrix(
+      page, landscape_bitmap_width, landscape_bitmap_height,
+      landscape_rotate_90_scale_2_matrix, landscape_bitmap_rect,
+      kLargerRotatedLandscapeMD5);
+
+  // On the larger bitmap, apply 45 degree rotation to a bitmap with the
+  // appropriate dimensions.
+  const float sqrt2 = 1.41421356f;
+  const int diagonal_bitmap_size = ceil((bitmap_width + bitmap_height) / sqrt2);
+  FS_RECTF diagonal_bitmap_rect{0, 0, diagonal_bitmap_size,
+                                diagonal_bitmap_size};
+  FS_MATRIX rotate_45_scale_2_matrix{
+      sqrt2, sqrt2, -sqrt2, sqrt2, bitmap_height / sqrt2, 0};
+  TestRenderPageBitmapWithMatrix(page, diagonal_bitmap_size,
+                                 diagonal_bitmap_size, rotate_45_scale_2_matrix,
+                                 diagonal_bitmap_rect,
+                                 kLargerRotatedDiagonalMD5);
+
+  // Render the (2, 1) tile of the page (third column, second row) when the page
+  // is divided in 50x50 pixel tiles. The tile is scaled by a factor of 7.
+  const float scale = 7.0;
+  const int tile_size = 50;
+  const int tile_x = 2;
+  const int tile_y = 1;
+  int tile_bitmap_size = scale * tile_size;
+  FS_RECTF tile_bitmap_rect{0, 0, tile_bitmap_size, tile_bitmap_size};
+  FS_MATRIX tile_2_1_matrix{scale,
+                            0,
+                            0,
+                            scale,
+                            -tile_x * tile_bitmap_size,
+                            -tile_y * tile_bitmap_size};
+  TestRenderPageBitmapWithMatrix(page, tile_bitmap_size, tile_bitmap_size,
+                                 tile_2_1_matrix, tile_bitmap_rect, kTileMD5);
 
   UnloadPage(page);
 }