src/chrome/browser/chromeos/login/screenshot_testing/SkDiffPixelsMetric_cpu.cpp

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // WARNING! This file is copied from third_party/skia/tools/skpdiff and slightly
   6 // modified to be compilable outside Skia and suit chromium style. Some comments
   7 // can make no sense.
   8 // TODO(elizavetai): remove this file and reuse the original one in Skia
   9
  10 #include "chrome/browser/chromeos/login/screenshot_testing/SkDiffPixelsMetric.h"
  11 #include "third_party/skia/include/core/SkBitmap.h"
  12
  13 bool SkDifferentPixelsMetric::diff(
  14     SkBitmap* baseline,
  15     SkBitmap* test,
  16     const SkImageDiffer::BitmapsToCreate& bitmapsToCreate,
  17     SkImageDiffer::Result* result) {
  18   // Ensure the images are comparable
  19   if (baseline->width() != test->width() ||
  20       baseline->height() != test->height() || baseline->width() <= 0 ||
  21       baseline->height() <= 0 || baseline->colorType() != test->colorType()) {
  22     DCHECK(baseline->width() == test->width());
  23     DCHECK(baseline->height() == test->height());
  24     DCHECK(baseline->width() > 0);
  25     DCHECK(baseline->height() > 0);
  26     DCHECK(baseline->colorType() == test->colorType());
  27     return false;
  28   }
  29
  30   int width = baseline->width();
  31   int height = baseline->height();
  32   int maxRedDiff = 0;
  33   int maxGreenDiff = 0;
  34   int maxBlueDiff = 0;
  35
  36   // Prepare any bitmaps we will be filling in
  37   if (bitmapsToCreate.alphaMask) {
  38     result->poiAlphaMask.allocPixels(SkImageInfo::MakeA8(width, height));
  39     result->poiAlphaMask.eraseARGB(SK_AlphaOPAQUE, 0, 0, 0);
  40   }
  41   if (bitmapsToCreate.rgbDiff) {
  42     result->rgbDiffBitmap.allocPixels(SkImageInfo::Make(
  43         width, height, baseline->colorType(), kPremul_SkAlphaType));
  44     result->rgbDiffBitmap.eraseARGB(SK_AlphaTRANSPARENT, 0, 0, 0);
  45   }
  46   if (bitmapsToCreate.whiteDiff) {
  47     result->whiteDiffBitmap.allocPixels(
  48         SkImageInfo::MakeN32Premul(width, height));
  49     result->whiteDiffBitmap.eraseARGB(SK_AlphaOPAQUE, 0, 0, 0);
  50   }
  51
  52   // Prepare the pixels for comparison
  53   result->poiCount = 0;
  54   baseline->lockPixels();
  55   test->lockPixels();
  56   for (int y = 0; y < height; y++) {
  57     // Grab a row from each image for easy comparison
  58     // TODO(epoger): The code below already assumes 4 bytes per pixel, so I
  59     // think
  60     // we could just call getAddr32() to save a little time.
  61     // OR, if we want to play it safe, call ComputeBytesPerPixel instead
  62     // of assuming 4 bytes per pixel.
  63     uint32_t* baselineRow = static_cast<uint32_t*>(baseline->getAddr(0, y));
  64     uint32_t* testRow = static_cast<uint32_t*>(test->getAddr(0, y));
  65     for (int x = 0; x < width; x++) {
  66       // Compare one pixel at a time so each differing pixel can be noted
  67       // TODO(epoger): This loop looks like a good place to work on performance,
  68       // but we should run the code through a profiler to be sure.
  69       uint32_t baselinePixel = baselineRow[x];
  70       uint32_t testPixel = testRow[x];
  71       if (baselinePixel != testPixel) {
  72         result->poiCount++;
  73
  74         int redDiff = abs(static_cast<int>(SkColorGetR(baselinePixel) -
  75                                            SkColorGetR(testPixel)));
  76         if (redDiff > maxRedDiff) {
  77           maxRedDiff = redDiff;
  78         }
  79         int greenDiff = abs(static_cast<int>(SkColorGetG(baselinePixel) -
  80                                              SkColorGetG(testPixel)));
  81         if (greenDiff > maxGreenDiff) {
  82           maxGreenDiff = greenDiff;
  83         }
  84         int blueDiff = abs(static_cast<int>(SkColorGetB(baselinePixel) -
  85                                             SkColorGetB(testPixel)));
  86         if (blueDiff > maxBlueDiff) {
  87           maxBlueDiff = blueDiff;
  88         }
  89
  90         if (bitmapsToCreate.alphaMask) {
  91           *result->poiAlphaMask.getAddr8(x, y) = SK_AlphaTRANSPARENT;
  92         }
  93         if (bitmapsToCreate.rgbDiff) {
  94           *result->rgbDiffBitmap.getAddr32(x, y) =
  95               SkColorSetRGB(redDiff, greenDiff, blueDiff);
  96         }
  97         if (bitmapsToCreate.whiteDiff) {
  98           *result->whiteDiffBitmap.getAddr32(x, y) = SK_ColorWHITE;
  99         }
 100       }
 101     }
 102   }
 103   test->unlockPixels();
 104   baseline->unlockPixels();
 105
 106   result->maxRedDiff = maxRedDiff;
 107   result->maxGreenDiff = maxGreenDiff;
 108   result->maxBlueDiff = maxBlueDiff;
 109
 110   if (bitmapsToCreate.alphaMask) {
 111     result->poiAlphaMask.unlockPixels();
 112   }
 113   if (bitmapsToCreate.rgbDiff) {
 114     result->rgbDiffBitmap.unlockPixels();
 115   }
 116   if (bitmapsToCreate.whiteDiff) {
 117     result->whiteDiffBitmap.unlockPixels();
 118   }
 119
 120   // Calculates the percentage of identical pixels
 121   result->result = 1.0 - ((double)result->poiCount / (width * height));
 122
 123   return true;
 124 }