Implement PDFiumPage::GenerateThumbnail()

Generate the thumbnail onto the SkBitmap of a Thumbnail object using
PDFium's FPDF_RenderPageBitmap().

Add a test PDF and expectation PNGs of its thumbnails at different
resolutions. Compare the rendered thumbnails to the expectation PNGs.

Bug: 652400
Change-Id: Id4c5e7f7a93822c6c38efdd63657e3e8002cd9cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382687Reviewed-by: Khushal <khushalsagar@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805961}

pdf/BUILD.gn

@@ -332,6 +332,7 @@ if (enable_pdf) {
       ":ppapi_migration",
       "//base",
       "//base/test:test_support",
+      "//cc:test_support",
       "//gin",
       "//ppapi/c",
       "//ppapi/cpp:objects",

pdf/pdfium/DEPS

 include_rules = [
+  "+cc/test/pixel_comparator.h",
+  "+cc/test/pixel_test_utils.h",
   "+gin/array_buffer.h",
   "+gin/public",
   "+gin/v8_initializer.h",

pdf/pdfium/pdfium_page.cc

@@ -23,11 +23,13 @@
 #include "pdf/pdfium/pdfium_engine.h"
 #include "pdf/pdfium/pdfium_unsupported_features.h"
 #include "pdf/ppapi_migration/geometry_conversions.h"
+#include "pdf/thumbnail.h"
 #include "ppapi/c/private/ppb_pdf.h"
 #include "printing/units.h"
 #include "third_party/pdfium/public/cpp/fpdf_scopers.h"
 #include "third_party/pdfium/public/fpdf_annot.h"
 #include "third_party/pdfium/public/fpdf_catalog.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
@@ -1457,6 +1459,34 @@ gfx::Rect PDFiumPage::PageToScreen(const gfx::Point& page_point,
                    new_size_y.ValueOrDie());
 }
 
+Thumbnail PDFiumPage::GenerateThumbnail(float device_pixel_ratio) {
+  DCHECK(available());
+
+  FPDF_PAGE page = GetPage();
+  gfx::Size page_size(base::saturated_cast<int>(FPDF_GetPageWidthF(page)),
+                      base::saturated_cast<int>(FPDF_GetPageHeightF(page)));
+  Thumbnail thumbnail(page_size, device_pixel_ratio);
+
+  SkBitmap& sk_bitmap = thumbnail.bitmap();
+  ScopedFPDFBitmap fpdf_bitmap(FPDFBitmap_CreateEx(
+      sk_bitmap.width(), sk_bitmap.height(), FPDFBitmap_BGRA,
+      sk_bitmap.getPixels(), sk_bitmap.rowBytes()));
+
+  // Clear the bitmap.
+  FPDFBitmap_FillRect(fpdf_bitmap.get(), /*left=*/0, /*top=*/0,
+                      sk_bitmap.width(), sk_bitmap.height(),
+                      /*color=*/0xFFFFFFFF);
+
+  // The combination of the |FPDF_REVERSE_BYTE_ORDER| rendering flag and the
+  // |FPDFBitmap_BGRA| format when initializing |fpdf_bitmap| results in an RGBA
+  // rendering, which is the format required by HTML <canvas>.
+  FPDF_RenderPageBitmap(fpdf_bitmap.get(), GetPage(), /*start_x=*/0,
+                        /*start_y=*/0, sk_bitmap.width(), sk_bitmap.height(),
+                        /*rotate=*/0, FPDF_ANNOT | FPDF_REVERSE_BYTE_ORDER);
+
+  return thumbnail;
+}
+
 PDFiumPage::ScopedUnloadPreventer::ScopedUnloadPreventer(PDFiumPage* page)
     : page_(page) {
   page_->preventing_unload_count_++;

pdf/pdfium/pdfium_page.h

@@ -30,6 +30,7 @@ class Point;
 namespace chrome_pdf {
 
 class PDFiumEngine;
+class Thumbnail;
 
 // Wrapper around a page from the document.
 class PDFiumPage {
@@ -157,6 +158,9 @@ class PDFiumPage {
                          double bottom,
                          PageOrientation orientation) const;
 
+  // Generate a page thumbnail accommodating a specific |device_pixel_ratio|.
+  Thumbnail GenerateThumbnail(float device_pixel_ratio);
+
   int index() const { return index_; }
 
   const gfx::Rect& rect() const { return rect_; }

pdf/pdfium/pdfium_page_unittest.cc

@@ -8,16 +8,23 @@
 #include <vector>
 
 #include "base/check.h"
+#include "base/files/file_path.h"
 #include "base/optional.h"
+#include "base/path_service.h"
 #include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/test/gtest_util.h"
+#include "cc/test/pixel_comparator.h"
+#include "cc/test/pixel_test_utils.h"
 #include "pdf/pdfium/pdfium_engine.h"
 #include "pdf/pdfium/pdfium_test_base.h"
 #include "pdf/test/test_client.h"
 #include "pdf/test/test_utils.h"
+#include "pdf/thumbnail.h"
 #include "ppapi/c/private/ppb_pdf.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/pdfium/public/fpdf_formfill.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/range/range.h"
 
@@ -73,6 +80,23 @@ void PopulateTextObjects(const std::vector<gfx::Range>& ranges,
   }
 }
 
+base::FilePath GetThumbnailTestData(const std::string& expectation_file_prefix,
+                                    size_t page_index,
+                                    float device_pixel_ratio) {
+  std::string file_dir = base::StringPrintf("%.1fx", device_pixel_ratio);
+  std::string file_name = base::StringPrintf(
+      "%s_expected.pdf.%zu.png", expectation_file_prefix.c_str(), page_index);
+  base::FilePath root_path;
+  if (!base::PathService::Get(base::DIR_SOURCE_ROOT, &root_path))
+    return base::FilePath();
+  return root_path.Append(FILE_PATH_LITERAL("pdf"))
+      .Append(FILE_PATH_LITERAL("test"))
+      .Append(FILE_PATH_LITERAL("data"))
+      .Append(FILE_PATH_LITERAL("thumbnail"))
+      .AppendASCII(file_dir)
+      .AppendASCII(file_name);
+}
+
 }  // namespace
 
 using PDFiumPageTest = PDFiumTestBase;
@@ -706,4 +730,64 @@ TEST_F(PDFiumPageOverlappingTest, CountCompleteOverlaps) {
   ASSERT_EQ(12u, PDFiumPage::CountLinkHighlightOverlaps(links, highlights));
 }
 
+class PDFiumPageThumbnailTest : public PDFiumTestBase {
+ public:
+  PDFiumPageThumbnailTest() = default;
+  PDFiumPageThumbnailTest(const PDFiumPageThumbnailTest&) = delete;
+  PDFiumPageThumbnailTest& operator=(const PDFiumPageThumbnailTest&) = delete;
+  ~PDFiumPageThumbnailTest() override = default;
+
+  void TestGenerateThumbnail(PDFiumEngine& engine,
+                             size_t page_index,
+                             float device_pixel_ratio,
+                             const gfx::Size& expected_thumbnail_size,
+                             const std::string& expectation_file_prefix) {
+    PDFiumPage& page = GetPDFiumPageForTest(engine, page_index);
+    Thumbnail thumbnail = page.GenerateThumbnail(device_pixel_ratio);
+    EXPECT_EQ(expected_thumbnail_size, gfx::Size(thumbnail.bitmap().width(),
+                                                 thumbnail.bitmap().height()));
+    EXPECT_EQ(device_pixel_ratio, thumbnail.device_pixel_ratio());
+
+    base::FilePath expectation_png_file_path = GetThumbnailTestData(
+        expectation_file_prefix, page_index, device_pixel_ratio);
+
+    cc::MatchesPNGFile(thumbnail.bitmap(), expectation_png_file_path,
+                       cc::ExactPixelComparator(/*discard_alpha=*/false));
+  }
+};
+
+TEST_F(PDFiumPageThumbnailTest, GenerateThumbnail) {
+  TestClient client;
+  std::unique_ptr<PDFiumEngine> engine =
+      InitializeEngine(&client, FILE_PATH_LITERAL("variable_page_sizes.pdf"));
+  ASSERT_EQ(7, engine->GetNumberOfPages());
+
+  static constexpr struct {
+    size_t page_index;
+    float device_pixel_ratio;
+    gfx::Size expected_thumbnail_size;
+  } kGenerateThumbnailTestParams[] = {
+      {0, 1, {108, 140}},  // ANSI Letter
+      {1, 1, {108, 152}},  // ISO 216 A4
+      {2, 1, {140, 140}},  // Square
+      {3, 1, {540, 108}},  // Wide
+      {4, 1, {108, 540}},  // Tall
+      {5, 1, {1399, 46}},  // Super wide
+      {6, 1, {46, 1399}},  // Super tall
+      {0, 2, {216, 280}},  // ANSI Letter
+      {1, 2, {214, 303}},  // ISO 216 A4
+      {2, 2, {255, 255}},  // Square
+      {3, 2, {571, 114}},  // Wide
+      {4, 2, {114, 571}},  // Tall
+      {5, 2, {1399, 46}},  // Super wide
+      {6, 2, {46, 1399}},  // Super tall
+  };
+
+  for (const auto& params : kGenerateThumbnailTestParams) {
+    TestGenerateThumbnail(*engine, params.page_index, params.device_pixel_ratio,
+                          params.expected_thumbnail_size,
+                          "variable_page_sizes");
+  }
+}
+
 }  // namespace chrome_pdf

pdf/test/data/thumbnail/README.md

+# PDF thumbnail test expectations
+
+The PNG files in this directory are the thumbnail rendering outputs for PDFs in
+`//pdf/test/data/`. They are generated from raw bitmaps using
+`gfx::PNGCodec::Encode()` using the `gfx::PNGCodec::FORMAT_RGBA` format. The
+PNGs are further optimized with `optipng`.
+
+Each PNG file is named using the PDF file name and zero-based page number, and
+is located in a directory corresponding to the device to pixel ratio. For
+example, the file located at `2.0x/variable_page_sizes_expected.pdf.3.png` is
+the thumbnail rendering of the fourth page of `variable_page_sizes.pdf` with a
+device to pixel ratio of 2.0.

pdf/test/data/variable_page_sizes.in

+{{header}}
+{{object 1 0}} <<
+  /Type /Catalog
+  /Pages 2 0 R
+>>
+endobj
+{{object 2 0}} <<
+  /Type /Pages
+  /Count 7
+  /Kids [3 0 R 4 0 R 5 0 R 6 0 R 7 0 R 8 0 R 9 0 R]
+>>
+endobj
+{{object 3 0}} <<
+  % ANSI Letter
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 612 792]
+  /Contents 10 0 R
+>>
+endobj
+{{object 4 0}} <<
+  % ISO 216 A4
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 595 842]
+  /Contents 10 0 R
+>>
+endobj
+{{object 5 0}} <<
+  % Square
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 200 200]
+  /Contents 10 0 R
+>>
+endobj
+{{object 6 0}} <<
+  % Wide
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 1000 200]
+  /Contents 10 0 R
+>>
+endobj
+{{object 7 0}} <<
+  % Tall
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 200 1000]
+  /Contents 10 0 R
+>>
+endobj
+{{object 8 0}} <<
+  % Super wide
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 1500 50]
+  /Contents 10 0 R
+>>
+endobj
+{{object 9 0}} <<
+  % Super tall
+  /Type /Page
+  /Parent 2 0 R
+  /MediaBox [0 0 50 1500]
+  /Contents 10 0 R
+>>
+endobj
+{{object 10 0}} <<
+  {{streamlen}}
+>>
+stream
+q
+0 0 1 rg
+0 0 25 25 re B*
+1 1 0 rg
+25 0 25 25 re B*
+1 0 0 rg
+0 25 25 25 re B*
+0 1 0 rg
+25 25 25 25 re B*
+Q
+endstream
+endobj
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF