Reland of r19131, this time with real Math:...

base/gfx/png_codec_unittest.cc

 // Copyright (c) 2006-2008 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 <math.h>
 
 #include "base/gfx/png_encoder.h"
 #include "base/gfx/png_decoder.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 
 static 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++) {
       unsigned char* org_px = &(*dat)[(y * w + x) * 3];
       org_px[0] = x * 3;      // r
       org_px[1] = x * 3 + 1;  // g
       org_px[2] = x * 3 + 2;  // b
     }
@@ skipping 14 matching lines @@
       org_px[1] = x * 3 + 1;  // g
       org_px[2] = x * 3 + 2;  // b
       if (use_transparency)
         org_px[3] = x*3 + 3;  // a
       else
         org_px[3] = 0xFF;     // a (opaque)
     }
   }
 }
 
+// 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) {
+  return abs(static_cast<int>(SkColorGetB(a) - SkColorGetB(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetG(a) - SkColorGetG(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetR(a) - SkColorGetR(b))) < 2 &&
+         abs(static_cast<int>(SkColorGetA(a) - SkColorGetA(b))) < 2;
+}
+
+void MakeTestSkBitmap(int w, int h, SkBitmap* bmp) {
+  bmp->setConfig(SkBitmap::kARGB_8888_Config, w, h);
+  bmp->allocPixels();
+
+  uint32_t* src_data = bmp->getAddr32(0, 0);
+  for (int i = 0; i < w * h; i++) {
+    src_data[i] = SkPreMultiplyARGB(i % 255, i % 250, i % 245, i % 240);
+  }
+}
+
 TEST(PNGCodec, EncodeDecodeRGB) {
   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;
   EXPECT_TRUE(PNGEncoder::Encode(&original[0], PNGEncoder::FORMAT_RGB, w, h,
@@ skipping 139 matching lines @@
   EXPECT_TRUE(PNGDecoder::Decode(&encoded[0], encoded.size(),
                                PNGDecoder::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_TRUE(original_rgb == decoded);
 }
+
+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;
+  PNGEncoder::EncodeBGRASkBitmap(original_bitmap, false, &encoded);
+
+  // Decode the encoded string.
+  SkBitmap decoded_bitmap;
+  EXPECT_TRUE(PNGDecoder::Decode(&encoded, &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 < w; x++) {
+    for (int y = 0; y < h; 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));
+    }
+  }
+}
+