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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <cstdlib>
#include "third_party/skia/include/core/SkBitmap.h"
#include "third_party/skia/include/core/SkColor.h"
namespace {
// Calculates how different two colors are, by comparing how far apart each of
// the RGBA channels are (in terms of percentages) and averaging that across all
// channels.
float ColorPercentDiff(SkColor color1, SkColor color2) {
float diff_red =
std::abs(static_cast<float>(SkColorGetR(color1)) - SkColorGetR(color2)) /
255.0f;
float diff_green =
std::abs(static_cast<float>(SkColorGetG(color1)) - SkColorGetG(color2)) /
255.0f;
float diff_blue =
std::abs(static_cast<float>(SkColorGetB(color1)) - SkColorGetB(color2)) /
255.0f;
float diff_alpha =
std::abs(static_cast<float>(SkColorGetA(color1)) - SkColorGetA(color2)) /
255.0f;
return (diff_red + diff_green + diff_blue + diff_alpha) / 4.0f;
}
} // namespace
namespace web_app {
bool HasMoreThanTenPercentImageDiff(const SkBitmap* before,
const SkBitmap* after) {
const bool before_null_or_empty = (before == nullptr || before->empty());
const bool after_null_or_empty = (after == nullptr || after->empty());
if (before_null_or_empty && after_null_or_empty) {
return false;
}
if (before_null_or_empty || after_null_or_empty) {
return true;
}
if (before->width() != after->width() ||
before->height() != after->height()) {
return true;
}
if (before->colorType() != after->colorType()) {
return true;
}
float difference = 0;
float num_pixels = static_cast<float>(before->height()) * before->width();
if (num_pixels == 0) {
return false;
}
// 10% of the total pixels that form the image
const float max_allowed_pixel_difference = 0.10f * num_pixels;
for (int y = 0; y < before->height(); ++y) {
for (int x = 0; x < before->width(); ++x) {
difference +=
ColorPercentDiff(before->getColor(x, y), after->getColor(x, y));
if (difference >= max_allowed_pixel_difference) {
return true;
}
}
}
return false;
}
} // namespace web_app
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