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/*
* Copyright (C) 2005, 2007-2021 Apple Inc. All rights reserved.
* Copyright (C) 2005 Ben La Monica <ben.lamonica@gmail.com>. All rights reserved.
* Copyright (C) 2011 Brent Fulgham. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "PlatformImage.h"
#include <algorithm>
#include <cstdlib>
namespace ImageDiff {
bool PlatformImage::isCompatible(const PlatformImage& other) const
{
return width() == other.width()
&& height() == other.height()
&& scaleFactor() == other.scaleFactor()
&& rowBytes() == other.rowBytes()
&& hasAlpha() == other.hasAlpha();
}
std::unique_ptr<PlatformImage> PlatformImage::difference(const PlatformImage& other, bool exact, Difference& difference)
{
size_t width = this->width();
size_t height = this->height();
// Compare the content of the 2 bitmaps
unsigned char* diffBuffer = static_cast<unsigned char*>(calloc(width * height, sizeof(unsigned char)));
size_t pixelCountWithSignificantDifference = 0;
float legacyDistanceSum = 0.0f;
float legacyDistanceMax = 0.0f;
unsigned char* basePixel = this->pixels();
unsigned char* pixel = other.pixels();
unsigned char* diffPixel = diffBuffer;
for (size_t y = 0; y < height; ++y) {
for (size_t x = 0; x < width; ++x) {
float red = (pixel[0] - basePixel[0]) / std::max<float>(255 - basePixel[0], basePixel[0]);
float green = (pixel[1] - basePixel[1]) / std::max<float>(255 - basePixel[1], basePixel[1]);
float blue = (pixel[2] - basePixel[2]) / std::max<float>(255 - basePixel[2], basePixel[2]);
float alpha = (pixel[3] - basePixel[3]) / std::max<float>(255 - basePixel[3], basePixel[3]);
float legacyDistance = sqrtf(red * red + green * green + blue * blue + alpha * alpha) / 2.0f;
// WPT-style difference code.
if (legacyDistance) {
++difference.totalPixels;
unsigned redDiff = std::abs(pixel[0] - basePixel[0]);
unsigned greenDiff = std::abs(pixel[1] - basePixel[1]);
unsigned blueDiff = std::abs(pixel[2] - basePixel[2]);
unsigned maxDiff = std::max({ redDiff, greenDiff, blueDiff });
difference.maxDifference = std::max(difference.maxDifference, maxDiff);
legacyDistanceMax = std::max(legacyDistanceMax, legacyDistance);
*diffPixel = static_cast<unsigned char>(std::ceil(legacyDistance * 255.0f));
}
// Legacy difference code.
bool pixelDiffers = exact ? legacyDistance : legacyDistance >= 1.0f / 255.0f;
if (pixelDiffers) {
++pixelCountWithSignificantDifference;
legacyDistanceSum += legacyDistance;
}
basePixel += 4;
pixel += 4;
++diffPixel;
}
}
// Compute the difference as a percentage combining both the number of different pixels and their difference amount i.e. the average distance over the entire image.
if (pixelCountWithSignificantDifference)
difference.percentageDifference = 100.0f * legacyDistanceSum / (height * width);
else
difference.percentageDifference = 0.0f;
if (difference.totalPixels) {
diffPixel = diffBuffer;
for (size_t p = 0; p < height * width; ++p) {
float pixel = static_cast<float>(diffPixel[p]);
if (!pixel)
continue;
pixel = std::min(pixel / legacyDistanceMax, 255.0f);
diffPixel[p] = static_cast<unsigned char>(pixel);
}
// totalPixels is "CSS pixels" or "points".
difference.totalPixels /= (scaleFactor() * scaleFactor());
return PlatformImage::createFromDiffData(diffBuffer, width, height);
}
free(diffBuffer);
return nullptr;
}
} // namespace ImageDiff