1/*
2 * Copyright (C) 2005, 2007, 2015 Apple Inc. All rights reserved.
3 * Copyright (C) 2005 Ben La Monica <ben.lamonica@gmail.com>. All rights reserved.
4 * Copyright (C) 2011 Brent Fulgham. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY
16 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
18 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR
19 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
23 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#include "PlatformImage.h"
29
30#include <algorithm>
31#include <cstdlib>
32
33namespace ImageDiff {
34
35bool PlatformImage::isCompatible(const PlatformImage& other) const
36{
37 return width() == other.width()
38 && height() == other.height()
39 && rowBytes() == other.rowBytes()
40 && hasAlpha() == other.hasAlpha();
41}
42
43std::unique_ptr<PlatformImage> PlatformImage::difference(const PlatformImage& other, float& percentageDifference)
44{
45 size_t width = this->width();
46 size_t height = this->height();
47
48 // Compare the content of the 2 bitmaps
49 void* diffBuffer = malloc(width * height);
50 float count = 0.0f;
51 float sum = 0.0f;
52 float maxDistance = 0.0f;
53 unsigned char* basePixel = this->pixels();
54 unsigned char* pixel = other.pixels();
55 unsigned char* diffPixel = reinterpret_cast<unsigned char*>(diffBuffer);
56 for (size_t y = 0; y < height; ++y) {
57 for (size_t x = 0; x < width; ++x) {
58 float red = (pixel[0] - basePixel[0]) / std::max<float>(255 - basePixel[0], basePixel[0]);
59 float green = (pixel[1] - basePixel[1]) / std::max<float>(255 - basePixel[1], basePixel[1]);
60 float blue = (pixel[2] - basePixel[2]) / std::max<float>(255 - basePixel[2], basePixel[2]);
61 float alpha = (pixel[3] - basePixel[3]) / std::max<float>(255 - basePixel[3], basePixel[3]);
62 float distance = sqrtf(red * red + green * green + blue * blue + alpha * alpha) / 2.0f;
63
64 *diffPixel++ = static_cast<unsigned char>(distance * 255.0f);
65
66 if (distance >= 1.0f / 255.0f) {
67 count += 1.0f;
68 sum += distance;
69 if (distance > maxDistance)
70 maxDistance = distance;
71 }
72
73 basePixel += 4;
74 pixel += 4;
75 }
76 }
77
78 // 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
79 if (count > 0.0f)
80 percentageDifference = 100.0f * sum / (height * width);
81 else
82 percentageDifference = 0.0f;
83
84 if (!percentageDifference) {
85 free(diffBuffer);
86 return nullptr;
87 }
88
89 // Generate a normalized diff image if there is any difference
90 if (maxDistance < 1.0f) {
91 diffPixel = reinterpret_cast<unsigned char*>(diffBuffer);
92 for (size_t p = 0; p < height * width; ++p)
93 diffPixel[p] /= maxDistance;
94 }
95
96 return PlatformImage::createFromDiffData(diffBuffer, width, height);
97}
98
99} // namespace ImageDiff
100