captureVisibleTab Extension API producing garbled PNG results

ui/gfx/codec/png_codec_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/logging.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/libpng/png.h"
@@ skipping 952 matching lines @@
                                PNGCodec::FORMAT_RGB, &decoded,
                                &outw, &outh));
 
   // It should be the same as our non-alpha-channel reference.
   ASSERT_EQ(w, outw);
   ASSERT_EQ(h, outh);
   ASSERT_EQ(original_rgb.size(), decoded.size());
   ASSERT_EQ(original_rgb, decoded);
 }
 
+TEST(PNGCodec, EncodeBGRASkBitmapStridePadded) {
+  const int kWidth = 20;
+  const int kHeight = 20;
+  const int kPaddedWidth = 32;
+  const int kBytesPerPixel = 4;
+  int paddedPixels = kPaddedWidth * kHeight;

[Alexei Svitkine (slow), 2013/03/05 22:28:55]

Please use either the kConstant or unix_hacker naming convention here. Make the
var const as well.

I suggest appending "size" to the name, since "pixels" sounds like the actual
buffer.

+  int rowBytes = kPaddedWidth * kBytesPerPixel;

[Alexei Svitkine (slow), 2013/03/05 22:28:55]

Please use either the kConstant or unix_hacker naming convention here. Make the
var const as well.

+
+  SkBitmap original_bitmap;
+  original_bitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                            kWidth, kHeight, rowBytes);
+  original_bitmap.allocPixels();
+
+  // Write data over the source bitmap.
+  // We write on the pad area here too.
+  // The encoder should ignore the pad area.
+  uint32_t* src_data = original_bitmap.getAddr32(0, 0);
+  for (int i = 0; i < paddedPixels; i++) {
+    src_data[i] = SkPreMultiplyARGB(i % 255, i % 250, i % 245, i % 240);
+  }
+
+  // Encode the bitmap.
+  std::vector<unsigned char> encoded;
+  PNGCodec::EncodeBGRASkBitmap(original_bitmap, false, &encoded);
+
+  // Decode the encoded string.
+  SkBitmap decoded_bitmap;
+  EXPECT_TRUE(PNGCodec::Decode(&encoded.front(), encoded.size(),
+                               &decoded_bitmap));
+
+  // Compare the original bitmap and the output bitmap. We use ColorsClose
+  // as SkBitmaps are considered to be pre-multiplied, the unpremultiplication
+  // (in Encode) and repremultiplication (in Decode) can be lossy.
+  for (int x = 0; x < kWidth; x++) {
+    for (int y = 0; y < kHeight; y++) {
+      uint32_t original_pixel = original_bitmap.getAddr32(0, y)[x];
+      uint32_t decoded_pixel = decoded_bitmap.getAddr32(0, y)[x];
+      EXPECT_TRUE(ColorsClose(original_pixel, decoded_pixel));
+    }
+  }
+}
+
 TEST(PNGCodec, EncodeBGRASkBitmap) {
   const int w = 20, h = 20;
 
   SkBitmap original_bitmap;
   MakeTestSkBitmap(w, h, &original_bitmap);
 
   // Encode the bitmap.
   std::vector<unsigned char> encoded;
   PNGCodec::EncodeBGRASkBitmap(original_bitmap, false, &encoded);
 
@@ skipping 128 matching lines @@
   ASSERT_EQ(w, outw);
   ASSERT_EQ(h, outh);
   ASSERT_EQ(original.size(), decoded.size());
 
   // Images must be exactly equal
   ASSERT_TRUE(original == decoded);
 }
 
 
 }  // namespace gfx