chromium/cc/test/pixel_comparator.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_TEST_PIXEL_COMPARATOR_H_
#define CC_TEST_PIXEL_COMPARATOR_H_

#include "base/compiler_specific.h"
#include "third_party/skia/include/core/SkBitmap.h"

namespace cc {

// Interface for pixel comparators.
class PixelComparator { … };

// Exact pixel comparator. Counts the number of pixel with an error.
class ExactPixelComparator : public PixelComparator { … };

class AlphaDiscardingExactPixelComparator : public ExactPixelComparator { … };

// Different platforms have slightly different pixel output, due to different
// graphics implementations. Slightly different pixels (in BGR space) are still
// counted as a matching pixel by this simple manhattan distance threshold.
// If, at any pixel, the sum of the absolute differences in each color component
// (excluding alpha) exceeds the threshold the test is failed.
class ManhattanDistancePixelComparator : public PixelComparator { … };

// Fuzzy pixel comparator. Counts small and arbitrary errors separately and
// computes average and maximum absolute errors per color channel. It can be
// configured to discard alpha channel. If alpha channel is not discarded
// (by default), alpha changing among fully transparent, translucent and fully
// opaque (e.g. 0 to 1, 254 to 255) are always reported.
class FuzzyPixelComparator : public PixelComparator { … };

// All pixels can be off by one, but any more than that is an error.
class FuzzyPixelOffByOneComparator : public FuzzyPixelComparator { … };

class AlphaDiscardingFuzzyPixelOffByOneComparator
    : public FuzzyPixelOffByOneComparator { … };
}  // namespace cc

#endif  // CC_TEST_PIXEL_COMPARATOR_H_