imageUtil.cpp

#include "imageUtil.h"

#include <QImage>

using namespace std;
namespace Color {
    const Real
        YCbCrCoeffs[][4]= {
            { 0.299,     0.587,     0.114,    0   },
            {-0.168736, -0.331264,  0.5,      0.5 },
            { 0.5,      -0.418688, -0.081312, 0.5 },
    
            { 1,         1,         1,        0   },
            { 0,        -0.34414,   1.772,   -0.5 },
            { 1.402,    -0.71414,   0,       -0.5 }
        },
        RGBCoeffs[][4]= {
            {1,0,0,0}, {0,1,0,0}, {0,0,1,0},
            {1,0,0,0}, {0,1,0,0}, {0,0,1,0}
        };
    
    vector<Real> getPSNR(const QImage &a,const QImage &b) {
        int width= a.width(), height= a.height();
        int x, y;
        QRgb *line1, *line2;
        long sum, sumR, sumG, sumB;
        sum= sumR= sumG= sumB= 0;
        for (y=0; y<height; ++y) { // \todo using walkers instead?
            line1= (QRgb*)a.scanLine(y);
            line2= (QRgb*)b.scanLine(y);
            for (x=0; x<width; ++x) {
                sum+= sqr( getGray(line1[x]) - getGray(line2[x]) );
                sumR+= sqr( qRed(line1[x]) - qRed(line2[x]) );
                sumG+= sqr( qGreen(line1[x]) - qGreen(line2[x]) );
                sumB+= sqr( qBlue(line1[x]) - qBlue(line2[x]) );
            }
        }
        vector<Real> result(4);
        result[0]= sumR;
        result[1]= sumG;
        result[2]= sumB;
        result[3]= sum;
        Real mul= Real(width*height) * Real(sqr(255));
        for (vector<Real>::iterator it=result.begin(); it!=result.end(); ++it)
            *it= Real(10) * log10(mul / *it);
        return result;
    }

} // Color namespace

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