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/**************************************************************************
*
* Copyright 2011 Jose Fonseca
* Copyright 2008-2010 VMware, Inc.
* All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*
**************************************************************************/
#include <assert.h>
#include <math.h>
#include <algorithm>
#include "image.hpp"
namespace image {
double Image::compare(Image &ref)
{
if (width != ref.width ||
height != ref.height ||
channels < 3 ||
ref.channels < 3) {
return 0.0;
}
// Ignore missing alpha when comparing RGB w/ RGBA, but enforce an equal
// number of channels otherwise.
unsigned minChannels = std::min(channels, ref.channels);
if (channels != ref.channels && minChannels < 3) {
return 0.0;
}
const unsigned char *pSrc = start();
const unsigned char *pRef = ref.start();
unsigned long long error = 0;
for (unsigned y = 0; y < height; ++y) {
for (unsigned x = 0; x < width; ++x) {
// FIXME: Ignore alpha channel until we are able to pick a visual
// that matches the traces
for (unsigned c = 0; c < minChannels; ++c) {
int delta = pSrc[x*channels + c] - pRef[x*ref.channels + c];
error += delta*delta;
}
}
pSrc += stride();
pRef += ref.stride();
}
double numerator = error*2 + 1;
double denominator = height*width*minChannels*255ULL*255ULL*2;
double quotient = numerator/denominator;
// Precision in bits
double precision = -log(quotient)/log(2.0);
return precision;
}
} /* namespace image */
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