Support for interlaced PNGs (in gfx::PNGCodec)

ui/gfx/codec/png_codec_unittest.cc

Index: ui/gfx/codec/png_codec_unittest.cc
===================================================================
--- ui/gfx/codec/png_codec_unittest.cc	(revision 123937)
+++ ui/gfx/codec/png_codec_unittest.cc	(working copy)
@@ -2,11 +2,19 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#if defined(USE_SYSTEM_LIBPNG)
+#include <png.h>
+#else
+#include "third_party/libpng/png.h"
+#endif

[Francois, 2012/02/28 15:00:36]

Required in order to encode interlaced, palette-based, and grayscale images (not
supported by PNGCodec::Encode). It was necessary to add tests for these types
because PNGCodec is actually used to decode such images.

+
 #include <algorithm>
 #include <cmath>
 
+#include "base/logging.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkColorPriv.h"
 #include "third_party/skia/include/core/SkUnPreMultiply.h"
 #include "third_party/zlib/zlib.h"
 #include "ui/gfx/codec/png_codec.h"
@@ -14,7 +22,9 @@
 
 namespace gfx {
 
-static void MakeRGBImage(int w, int h, std::vector<unsigned char>* dat) {
+namespace {
+
+void MakeRGBImage(int w, int h, std::vector<unsigned char>* dat) {
   dat->resize(w * h * 3);
   for (int y = 0; y < h; y++) {
     for (int x = 0; x < w; x++) {
@@ -30,8 +40,8 @@
 // be filled with 0xff. With the alpha channel stripped, this should yield the
 // same image as MakeRGBImage above, so the code below can make reference
 // images for conversion testing.
-static void MakeRGBAImage(int w, int h, bool use_transparency,
-                          std::vector<unsigned char>* dat) {
+void MakeRGBAImage(int w, int h, bool use_transparency,
+                   std::vector<unsigned char>* dat) {
   dat->resize(w * h * 4);
   for (int y = 0; y < h; y++) {
     for (int x = 0; x < w; x++) {
@@ -47,6 +57,188 @@
   }
 }
 
+// Creates a palette-based image.
+void MakePaletteImage(int w, int h,
+                      std::vector<unsigned char>* dat,
+                      std::vector<png_color>* palette,
+                      std::vector<unsigned char>* trans_chunk = 0) {
+  dat->resize(w * h);
+  palette->resize(w);
+  for (int i = 0; i < w; ++i) {
+    png_color& color = (*palette)[i];
+    color.red = i * 3;
+    color.green = color.red + 1;
+    color.blue = color.red + 2;
+  }
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      (*dat)[y * w + x] = x;  // palette index
+    }
+  }
+  if (trans_chunk) {
+    trans_chunk->resize(palette->size());
+    for (std::size_t i = 0; i < trans_chunk->size(); ++i) {
+      (*trans_chunk)[i] = i % 256;
+    }
+  }
+}
+
+// Creates a grayscale image without an alpha channel.
+void MakeGrayscaleImage(int w, int h,
+                        std::vector<unsigned char>* dat) {
+  dat->resize(w * h);
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      (*dat)[y * w + x] = x;  // gray value
+    }
+  }
+}
+
+// Creates a grayscale image with an alpha channel.
+void MakeGrayscaleAlphaImage(int w, int h,
+                             std::vector<unsigned char>* dat) {
+  dat->resize(w * h * 2);
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      unsigned char* px = &(*dat)[(y * w + x) * 2];
+      px[0] = x;        // gray value
+      px[1] = x % 256;  // alpha
+    }
+  }
+}
+
+// User write function (to be passed to libpng by EncodeImage) which writes
+// into a buffer instead of to a file.
+void WriteImageData(png_structp png_ptr,
+                    png_bytep data,
+                    png_size_t length) {
+  std::vector<unsigned char>& v =
+      *static_cast<std::vector<unsigned char>*>(png_get_io_ptr(png_ptr));
+  v.resize(v.size() + length);
+  memcpy(&v[v.size() - length], data, length);
+}
+
+// User flush function; goes with WriteImageData, above.
+void FlushImageData(png_structp) {}

[Francois, 2012/02/28 15:00:36]

Will change this to void FlushImageData(png_structp /*png_ptr*/) {} when I
upload the next patch set.

[Francois, 2012/02/29 09:12:29]

Done.

+
+// Libpng user error function which allows us to print libpng errors using
+// Chrome's logging facilities instead of stderr.
+void LogLibPNGError(png_structp png_ptr,
+                    png_const_charp error_msg) {
+  DLOG(ERROR) << "libpng encode error: " << error_msg;
+  longjmp(png_jmpbuf(png_ptr), 1);
+}
+
+// Goes with LogLibPNGError, above.
+void LogLibPNGWarning(png_structp png_ptr,
+                      png_const_charp warning_msg) {
+  DLOG(ERROR) << "libpng encode warning: " << warning_msg;
+}
+
+// Color types supported by EncodeImage. Required because neither libpng nor
+// PNGCodec::Encode supports all of the required values.
+enum ColorType {
+  COLOR_TYPE_GRAY = PNG_COLOR_TYPE_GRAY,
+  COLOR_TYPE_GRAY_ALPHA = PNG_COLOR_TYPE_GRAY_ALPHA,
+  COLOR_TYPE_PALETTE = PNG_COLOR_TYPE_PALETTE,
+  COLOR_TYPE_RGB = PNG_COLOR_TYPE_RGB,
+  COLOR_TYPE_RGBA = PNG_COLOR_TYPE_RGBA,
+  COLOR_TYPE_BGR,
+  COLOR_TYPE_BGRA
+};
+
+// PNG encoder used for testing. Required because PNGCodec::Encode doesn't do
+// interlaced, palette-based, or grayscale images, but PNGCodec::Decode is
+// actually asked to decode these types of images by Chrome.
+bool EncodeImage(const std::vector<unsigned char>& input,
+                 const int width,
+                 const int height,
+                 ColorType output_color_type,
+                 std::vector<unsigned char>* output,
+                 const int interlace_type = PNG_INTERLACE_NONE,
+                 std::vector<png_color>* palette = 0,
+                 std::vector<unsigned char>* palette_alpha = 0) {
+  struct ScopedPNGStructs {
+    ScopedPNGStructs(png_struct** s, png_info** i) : s_(s), i_(i) {}
+    ~ScopedPNGStructs() { png_destroy_write_struct(s_, i_); }
+    png_struct** s_;
+    png_info** i_;
+  };
+
+  DCHECK(output);
+  png_struct* png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
+                                                NULL, NULL, NULL);
+  if (!png_ptr) return false;
+
+  png_infop info_ptr = png_create_info_struct(png_ptr);
+  if (!info_ptr) {
+    png_destroy_write_struct(&png_ptr, NULL);
+    return false;
+  }
+
+  ScopedPNGStructs scoped_png_structs(&png_ptr, &info_ptr);
+
+  if (setjmp(png_jmpbuf(png_ptr)))
+    return false;
+
+  png_set_error_fn(png_ptr, NULL, LogLibPNGError, LogLibPNGWarning);
+
+  int input_rowbytes = 0;
+  int transforms = PNG_TRANSFORM_IDENTITY;
+
+  switch (output_color_type) {
+    case COLOR_TYPE_GRAY:
+      input_rowbytes = width;
+      break;
+    case COLOR_TYPE_GRAY_ALPHA:
+      input_rowbytes = width * 2;
+      break;
+    case COLOR_TYPE_PALETTE:
+      if (!palette) return false;
+      input_rowbytes = width;
+      break;
+    case COLOR_TYPE_RGB:
+      input_rowbytes = width * 3;
+      break;
+    case COLOR_TYPE_RGBA:
+      input_rowbytes = width * 4;
+      break;
+    case COLOR_TYPE_BGRA:
+      input_rowbytes = width * 4;
+      output_color_type = static_cast<ColorType>(PNG_COLOR_TYPE_RGBA);
+      transforms |= PNG_TRANSFORM_BGR;
+      break;
+    default:
+      return false;
+      break;
+  };
+
+  std::vector<png_bytep> row_pointers(height);
+  for (int y = 0 ; y < height; y++) {
+    row_pointers[y] = const_cast<unsigned char*>(&input[y * input_rowbytes]);
+  }
+  png_set_rows(png_ptr, info_ptr, &row_pointers[0]);
+  png_set_write_fn(png_ptr, output, WriteImageData, FlushImageData);
+  png_set_IHDR(png_ptr, info_ptr, width, height, 8, output_color_type,
+               interlace_type, PNG_COMPRESSION_TYPE_DEFAULT,
+               PNG_FILTER_TYPE_DEFAULT);
+  if (output_color_type == COLOR_TYPE_PALETTE) {
+    png_set_PLTE(png_ptr, info_ptr, &palette->front(), palette->size());
+    if (palette_alpha)
+      png_set_tRNS(png_ptr,
+                   info_ptr,
+                   &palette_alpha->front(),
+                   palette_alpha->size(),
+                   NULL);
+  }
+
+  png_write_png(png_ptr, info_ptr, transforms, NULL);
+
+  return true;
+}
+
+}  // namespace
+
 // Returns true if each channel of the given two colors are "close." This is
 // used for comparing colors where rounding errors may cause off-by-one.
 bool ColorsClose(uint32_t a, uint32_t b) {
@@ -82,7 +274,7 @@
 
   // encode
   std::vector<unsigned char> encoded;
-  EXPECT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGB,
+  ASSERT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGB,
                                Size(w, h), w * 3, false,
                                std::vector<PNGCodec::Comment>(),
                                &encoded));
@@ -90,7 +282,7 @@
   // decode, it should have the same size as the original
   std::vector<unsigned char> decoded;
   int outw, outh;
-  EXPECT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
                                PNGCodec::FORMAT_RGB, &decoded,
                                &outw, &outh));
   ASSERT_EQ(w, outw);
@@ -111,7 +303,7 @@
 
   // encode
   std::vector<unsigned char> encoded;
-  EXPECT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGBA,
+  ASSERT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGBA,
                                Size(w, h), w * 4, false,
                                std::vector<PNGCodec::Comment>(),
                                &encoded));
@@ -119,7 +311,7 @@
   // decode, it should have the same size as the original
   std::vector<unsigned char> decoded;
   int outw, outh;
-  EXPECT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
                                PNGCodec::FORMAT_RGBA, &decoded,
                                &outw, &outh));
   ASSERT_EQ(w, outw);
@@ -130,6 +322,505 @@
   ASSERT_TRUE(original == decoded);
 }
 
+TEST(PNGCodec, EncodeDecodeBGRA) {
+  const int w = 20, h = 20;
+
+  // Create an image with known values, alpha must be opaque because it will be
+  // lost during encoding.
+  std::vector<unsigned char> original;
+  MakeRGBAImage(w, h, true, &original);
+
+  // Encode.
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_BGRA,
+                               Size(w, h), w * 4, false,
+                               std::vector<PNGCodec::Comment>(),
+                               &encoded));
+
+  // Decode, it should have the same size as the original.
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_BGRA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(original.size(), decoded.size());
+
+  // Images must be exactly equal.
+  ASSERT_TRUE(original == decoded);
+}

[Francois, 2012/02/28 15:00:36]

Old code moved from further down.

+
+TEST(PNGCodec, DecodePalette) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  std::vector<png_color> original_palette;
+  std::vector<unsigned char> original_trans_chunk;
+  MakePaletteImage(w, h, &original, &original_palette, &original_trans_chunk);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_PALETTE,
+                          &encoded,
+                          PNG_INTERLACE_NONE,
+                          &original_palette,
+                          &original_trans_chunk));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), w * h * 4U);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char palette_pixel = original[y * w + x];
+      png_color& palette_color = original_palette[palette_pixel];
+      int alpha = original_trans_chunk[palette_pixel];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 4];
+
+      ASSERT_EQ(palette_color.red, rgba_pixel[0]);
+      ASSERT_EQ(palette_color.green, rgba_pixel[1]);
+      ASSERT_EQ(palette_color.blue, rgba_pixel[2]);
+      ASSERT_EQ(alpha, rgba_pixel[3]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodePaletteDiscardAlpha) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  std::vector<png_color> original_palette;
+  std::vector<unsigned char> original_trans_chunk;
+  MakePaletteImage(w, h, &original, &original_palette, &original_trans_chunk);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_PALETTE,
+                          &encoded,
+                          PNG_INTERLACE_NONE,
+                          &original_palette,
+                          &original_trans_chunk));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGB, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), w * h * 3U);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char palette_pixel = original[y * w + x];
+      png_color& palette_color = original_palette[palette_pixel];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 3];
+
+      ASSERT_EQ(palette_color.red, rgba_pixel[0]);
+      ASSERT_EQ(palette_color.green, rgba_pixel[1]);
+      ASSERT_EQ(palette_color.blue, rgba_pixel[2]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeInterlacedPalette) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  std::vector<png_color> original_palette;
+  std::vector<unsigned char> original_trans_chunk;
+  MakePaletteImage(w, h, &original, &original_palette, &original_trans_chunk);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_PALETTE,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7,
+                          &original_palette,
+                          &original_trans_chunk));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), w * h * 4U);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char palette_pixel = original[y * w + x];
+      png_color& palette_color = original_palette[palette_pixel];
+      int alpha = original_trans_chunk[palette_pixel];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 4];
+
+      ASSERT_EQ(palette_color.red, rgba_pixel[0]);
+      ASSERT_EQ(palette_color.green, rgba_pixel[1]);
+      ASSERT_EQ(palette_color.blue, rgba_pixel[2]);
+      ASSERT_EQ(alpha, rgba_pixel[3]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeGrayscale) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeGrayscaleImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original, w, h, COLOR_TYPE_GRAY, &encoded));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGB, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), original.size() * 3);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char gray_pixel = original[(y * w + x)];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 3];
+      ASSERT_EQ(rgba_pixel[0], gray_pixel);
+      ASSERT_EQ(rgba_pixel[1], gray_pixel);
+      ASSERT_EQ(rgba_pixel[2], gray_pixel);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeGrayscaleWithAlpha) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeGrayscaleAlphaImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_GRAY_ALPHA,
+                          &encoded));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), original.size() * 2);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char* gray_pixel = &original[(y * w + x) * 2];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 4];
+      ASSERT_EQ(rgba_pixel[0], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[1], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[2], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[3], gray_pixel[1]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeGrayscaleWithAlphaDiscardAlpha) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeGrayscaleAlphaImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_GRAY_ALPHA,
+                          &encoded));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGB, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), w * h * 3U);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char* gray_pixel = &original[(y * w + x) * 2];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 3];
+      ASSERT_EQ(rgba_pixel[0], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[1], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[2], gray_pixel[0]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeInterlacedGrayscale) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeGrayscaleImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_GRAY,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), original.size() * 4);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char gray_pixel = original[(y * w + x)];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 4];
+      ASSERT_EQ(rgba_pixel[0], gray_pixel);
+      ASSERT_EQ(rgba_pixel[1], gray_pixel);
+      ASSERT_EQ(rgba_pixel[2], gray_pixel);
+      ASSERT_EQ(rgba_pixel[3], 0xFF);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeInterlacedGrayscaleWithAlpha) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeGrayscaleAlphaImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_GRAY_ALPHA,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // decode
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(decoded.size(), original.size() * 2);
+
+  // Images must be equal
+  for (int y = 0; y < h; ++y) {
+    for (int x = 0; x < w; ++x) {
+      unsigned char* gray_pixel = &original[(y * w + x) * 2];
+      unsigned char* rgba_pixel = &decoded[(y * w + x) * 4];
+      ASSERT_EQ(rgba_pixel[0], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[1], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[2], gray_pixel[0]);
+      ASSERT_EQ(rgba_pixel[3], gray_pixel[1]);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeInterlacedRGB) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeRGBImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_RGB,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // decode, it should have the same size as the original
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGB, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(original.size(), decoded.size());
+
+  // Images must be equal
+  ASSERT_EQ(original, decoded);
+}
+
+TEST(PNGCodec, DecodeInterlacedRGBA) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeRGBAImage(w, h, false, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_RGBA,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // decode, it should have the same size as the original
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_RGBA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(original.size(), decoded.size());
+
+  // Images must be equal
+  ASSERT_EQ(original, decoded);
+}
+
+TEST(PNGCodec, DecodeInterlacedBGRA) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeRGBAImage(w, h, false, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_BGRA,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // decode, it should have the same size as the original
+  std::vector<unsigned char> decoded;
+  int outw, outh;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
+                               PNGCodec::FORMAT_BGRA, &decoded,
+                               &outw, &outh));
+  ASSERT_EQ(w, outw);
+  ASSERT_EQ(h, outh);
+  ASSERT_EQ(original.size(), decoded.size());
+
+  // Images must be equal
+  ASSERT_EQ(original, decoded);
+}
+
+// Not encoding an interlaced PNG from SkBitmap because we don't do it
+// anywhere, and the ability to do that requires more code changes.
+TEST(PNGCodec, DecodeInterlacedRGBtoSkBitmap) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeRGBImage(w, h, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_RGB,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // Decode the encoded string.
+  SkBitmap decoded_bitmap;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded.front(), encoded.size(),
+                               &decoded_bitmap));
+
+  for (int x = 0; x < w; x++) {
+    for (int y = 0; y < h; y++) {
+      const unsigned char* original_pixel = &original[(y * w + x) * 3];
+      const uint32_t original_pixel_sk = SkPackARGB32(0xFF,
+                                                      original_pixel[0],
+                                                      original_pixel[1],
+                                                      original_pixel[2]);
+      const uint32_t decoded_pixel = decoded_bitmap.getAddr32(0, y)[x];
+      ASSERT_EQ(original_pixel_sk, decoded_pixel);
+    }
+  }
+}
+
+TEST(PNGCodec, DecodeInterlacedRGBAtoSkBitmap) {
+  const int w = 20, h = 20;
+
+  // create an image with known values
+  std::vector<unsigned char> original;
+  MakeRGBAImage(w, h, false, &original);
+
+  // encode
+  std::vector<unsigned char> encoded;
+  ASSERT_TRUE(EncodeImage(original,
+                          w, h,
+                          COLOR_TYPE_RGBA,
+                          &encoded,
+                          PNG_INTERLACE_ADAM7));
+
+  // Decode the encoded string.
+  SkBitmap decoded_bitmap;
+  ASSERT_TRUE(PNGCodec::Decode(&encoded.front(), encoded.size(),
+                               &decoded_bitmap));
+
+  for (int x = 0; x < w; x++) {
+    for (int y = 0; y < h; y++) {
+      const unsigned char* original_pixel = &original[(y * w + x) * 4];
+      const uint32_t original_pixel_sk = SkPackARGB32(original_pixel[3],
+                                                      original_pixel[0],
+                                                      original_pixel[1],
+                                                      original_pixel[2]);
+      const uint32_t decoded_pixel = decoded_bitmap.getAddr32(0, y)[x];
+      ASSERT_EQ(original_pixel_sk, decoded_pixel);
+    }
+  }
+}
+
 // Test that corrupted data decompression causes failures.
 TEST(PNGCodec, DecodeCorrupted) {
   int w = 20, h = 20;
@@ -147,7 +838,7 @@
 
   // Make some compressed data.
   std::vector<unsigned char> compressed;
-  EXPECT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGB,
+  ASSERT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_RGB,
                                Size(w, h), w * 3, false,
                                std::vector<PNGCodec::Comment>(),
                                &compressed));
@@ -165,35 +856,6 @@
                                 &outw, &outh));
 }
 
-TEST(PNGCodec, EncodeDecodeBGRA) {
-  const int w = 20, h = 20;
-
-  // Create an image with known values, alpha must be opaque because it will be
-  // lost during encoding.
-  std::vector<unsigned char> original;
-  MakeRGBAImage(w, h, true, &original);
-
-  // Encode.
-  std::vector<unsigned char> encoded;
-  EXPECT_TRUE(PNGCodec::Encode(&original[0], PNGCodec::FORMAT_BGRA,
-                               Size(w, h), w * 4, false,
-                               std::vector<PNGCodec::Comment>(),
-                               &encoded));
-
-  // Decode, it should have the same size as the original.
-  std::vector<unsigned char> decoded;
-  int outw, outh;
-  EXPECT_TRUE(PNGCodec::Decode(&encoded[0], encoded.size(),
-                               PNGCodec::FORMAT_BGRA, &decoded,
-                               &outw, &outh));
-  ASSERT_EQ(w, outw);
-  ASSERT_EQ(h, outh);
-  ASSERT_EQ(original.size(), decoded.size());
-
-  // Images must be exactly equal.
-  ASSERT_TRUE(original == decoded);

[Francois, 2012/02/28 15:00:36]

This function was moved further up.

-}
-
 TEST(PNGCodec, StripAddAlpha) {
   const int w = 20, h = 20;
 
@@ -221,7 +883,7 @@
   ASSERT_EQ(w, outw);
   ASSERT_EQ(h, outh);
   ASSERT_EQ(original_rgba.size(), decoded.size());
-  ASSERT_TRUE(original_rgba == decoded);
+  ASSERT_EQ(original_rgba, decoded);
 
   // Encode RGBA to RGBA.
   EXPECT_TRUE(PNGCodec::Encode(&original_rgba[0], PNGCodec::FORMAT_RGBA,
@@ -238,7 +900,7 @@
   ASSERT_EQ(w, outw);
   ASSERT_EQ(h, outh);
   ASSERT_EQ(original_rgb.size(), decoded.size());
-  ASSERT_TRUE(original_rgb == decoded);
+  ASSERT_EQ(original_rgb, decoded);
 }
 
 TEST(PNGCodec, EncodeBGRASkBitmap) {