Fix image mask area calculations used by FPDF_RenderPage().
Inside FPDF_RenderPage(), when it encounters an image mask, it falls
back to rasterizing the entire PDF to ensure correctness. There is a
disabled implementation to only rasterize the areas of the page that
contains image masks. This code is disabled because it contains a bug
that causes missing content.
In particular, GetMaskBitmap() calls GetMaskDimensionsAndOffsets() to
figure out where the image mask is. The input for the image mask area
is in the user (page) coordinate space, but the output needs to be in
the device coordinate space. GetMaskDimensionsAndOffsets() does not
always do this transformation correctly, so remove it entirely. Instead,
use CPDF_Page::GetDisplayMatrix() to get the correct transformation
matrix and apply it.
Bug: chromium:674771
Change-Id: Ic827a8f82e3e896e5120f70b51be7bfd149c4ca0
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/69733
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
diff --git a/fpdfsdk/fpdf_view.cpp b/fpdfsdk/fpdf_view.cpp
index e838e49..e7e2735 100644
--- a/fpdfsdk/fpdf_view.cpp
+++ b/fpdfsdk/fpdf_view.cpp
@@ -6,6 +6,7 @@
#include "public/fpdfview.h"
+#include <cmath>
#include <memory>
#include <utility>
#include <vector>
@@ -343,81 +344,24 @@
#if defined(OS_WIN)
namespace {
-const double kEpsilonSize = 0.01f;
+constexpr float kEpsilonSize = 0.01f;
-void GetScaling(CPDF_Page* pPage,
- int size_x,
- int size_y,
- int rotate,
- double* scale_x,
- double* scale_y) {
- ASSERT(pPage);
- ASSERT(scale_x);
- ASSERT(scale_y);
- double page_width = pPage->GetPageWidth();
- double page_height = pPage->GetPageHeight();
- if (page_width < kEpsilonSize || page_height < kEpsilonSize)
- return;
-
- if (rotate % 2 == 0) {
- *scale_x = size_x / page_width;
- *scale_y = size_y / page_height;
- } else {
- *scale_x = size_y / page_width;
- *scale_y = size_x / page_height;
- }
+bool IsPageTooSmall(const CPDF_Page* page) {
+ const CFX_SizeF& page_size = page->GetPageSize();
+ return page_size.width < kEpsilonSize || page_size.height < kEpsilonSize;
}
-FX_RECT GetMaskDimensionsAndOffsets(CPDF_Page* pPage,
- int start_x,
- int start_y,
- int size_x,
- int size_y,
- int rotate,
- const CFX_FloatRect& mask_box) {
- double scale_x = 0.0f;
- double scale_y = 0.0f;
- GetScaling(pPage, size_x, size_y, rotate, &scale_x, &scale_y);
- if (scale_x < kEpsilonSize || scale_y < kEpsilonSize)
- return FX_RECT();
-
- // Compute sizes in page points. Round down to catch the entire bitmap.
- int start_x_bm = static_cast<int>(mask_box.left * scale_x);
- int start_y_bm = static_cast<int>(mask_box.bottom * scale_y);
- int size_x_bm = static_cast<int>(mask_box.right * scale_x + 1.0f) -
- static_cast<int>(mask_box.left * scale_x);
- int size_y_bm = static_cast<int>(mask_box.top * scale_y + 1.0f) -
- static_cast<int>(mask_box.bottom * scale_y);
-
- // Get page rotation
- int page_rotation = pPage->GetPageRotation();
-
- // Compute offsets
- int offset_x = 0;
- int offset_y = 0;
- if (size_x > size_y)
- std::swap(size_x_bm, size_y_bm);
-
- switch ((rotate + page_rotation) % 4) {
- case 0:
- offset_x = start_x_bm + start_x;
- offset_y = start_y + size_y - size_y_bm - start_y_bm;
- break;
- case 1:
- offset_x = start_y_bm + start_x;
- offset_y = start_x_bm + start_y;
- break;
- case 2:
- offset_x = start_x + size_x - size_x_bm - start_x_bm;
- offset_y = start_y_bm + start_y;
- break;
- case 3:
- offset_x = start_x + size_x - size_x_bm - start_y_bm;
- offset_y = start_y + size_y - size_y_bm - start_x_bm;
- break;
+bool IsScalingTooSmall(const CFX_Matrix& matrix) {
+ float horizontal;
+ float vertical;
+ if (matrix.a == 0.0f && matrix.d == 0.0f) {
+ horizontal = matrix.b;
+ vertical = matrix.c;
+ } else {
+ horizontal = matrix.a;
+ vertical = matrix.d;
}
- return FX_RECT(offset_x, offset_y, offset_x + size_x_bm,
- offset_y + size_y_bm);
+ return fabsf(horizontal) < kEpsilonSize || fabsf(vertical) < kEpsilonSize;
}
// Get a bitmap of just the mask section defined by |mask_box| from a full page
@@ -431,9 +375,15 @@
const RetainPtr<CFX_DIBitmap>& pSrc,
const CFX_FloatRect& mask_box,
FX_RECT* bitmap_area) {
- ASSERT(bitmap_area);
- *bitmap_area = GetMaskDimensionsAndOffsets(pPage, start_x, start_y, size_x,
- size_y, rotate, mask_box);
+ if (IsPageTooSmall(pPage))
+ return nullptr;
+
+ FX_RECT page_rect(start_x, start_y, start_x + size_x, start_y + size_y);
+ CFX_Matrix matrix = pPage->GetDisplayMatrix(page_rect, rotate);
+ if (IsScalingTooSmall(matrix))
+ return nullptr;
+
+ *bitmap_area = matrix.TransformRect(mask_box).GetOuterRect();
if (bitmap_area->IsEmpty())
return nullptr;
