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/*
* The equivalent of Zhou Wang's SSIM matlab code using OpenCV.
* from http://www.cns.nyu.edu/~zwang/files/research/ssim/index.html
* The measure is described in :
* "Image quality assessment: From error measurement to structural similarity"
* C++ code by Rabah Mehdi. http://mehdi.rabah.free.fr/SSIM
*
* This implementation is under the public domain.
* @see http://creativecommons.org/licenses/publicdomain/
* The original work may be under copyrights.
*/
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <iostream>
/*
* Parameters : complete path to the two image to be compared
* The file format must be supported by your OpenCV build
*/
#if 0
int main(int argc, char** argv)
{
if(argc!=3)
return -1;
}
#endif
long double
ssim(char const *fn1, char const *fn2)
{
// default settings
const double K1 = 0.01;
const double K2 = 0.03;
const int L = 255;
const double C1 = (K1 * L) * (K1 * L); //6.5025 C1 = (K(1)*L)^2;
const double C2 = (K2 * L) * (K2 * L); //58.5225 C2 = (K(2)*L)^2;
IplImage
*img1=NULL, *img2=NULL, *img1_img2=NULL,
*img1_temp=NULL, *img2_temp=NULL,
*img1_sq=NULL, *img2_sq=NULL,
*mu1=NULL, *mu2=NULL,
*mu1_sq=NULL, *mu2_sq=NULL, *mu1_mu2=NULL,
*sigma1_sq=NULL, *sigma2_sq=NULL, *sigma12=NULL,
*ssim_map=NULL, *temp1=NULL, *temp2=NULL, *temp3=NULL;
/***************************** INITS **********************************/
img1_temp = cvLoadImage(fn1, CV_LOAD_IMAGE_GRAYSCALE);
img2_temp = cvLoadImage(fn2, CV_LOAD_IMAGE_GRAYSCALE);
if(img1_temp==NULL || img2_temp==NULL)
return -1;
int x=img1_temp->width, y=img1_temp->height;
int nChan=1, d=IPL_DEPTH_32F;
CvSize size = cvSize(x, y);
img1 = cvCreateImage( size, d, nChan);
img2 = cvCreateImage( size, d, nChan);
cvConvert(img1_temp, img1);
cvConvert(img2_temp, img2);
cvReleaseImage(&img1_temp);
cvReleaseImage(&img2_temp);
img1_sq = cvCreateImage( size, d, nChan);
img2_sq = cvCreateImage( size, d, nChan);
img1_img2 = cvCreateImage( size, d, nChan);
cvPow( img1, img1_sq, 2 );
cvPow( img2, img2_sq, 2 );
cvMul( img1, img2, img1_img2, 1 );
mu1 = cvCreateImage( size, d, nChan);
mu2 = cvCreateImage( size, d, nChan);
mu1_sq = cvCreateImage( size, d, nChan);
mu2_sq = cvCreateImage( size, d, nChan);
mu1_mu2 = cvCreateImage( size, d, nChan);
sigma1_sq = cvCreateImage( size, d, nChan);
sigma2_sq = cvCreateImage( size, d, nChan);
sigma12 = cvCreateImage( size, d, nChan);
temp1 = cvCreateImage( size, d, nChan);
temp2 = cvCreateImage( size, d, nChan);
temp3 = cvCreateImage( size, d, nChan);
ssim_map = cvCreateImage( size, d, nChan);
/*************************** END INITS **********************************/
//////////////////////////////////////////////////////////////////////////
// PRELIMINARY COMPUTING
cvSmooth( img1, mu1, CV_GAUSSIAN, 11, 11, 1.5 );
cvSmooth( img2, mu2, CV_GAUSSIAN, 11, 11, 1.5 );
cvPow( mu1, mu1_sq, 2 );
cvPow( mu2, mu2_sq, 2 );
cvMul( mu1, mu2, mu1_mu2, 1 );
cvSmooth( img1_sq, sigma1_sq, CV_GAUSSIAN, 11, 11, 1.5 );
cvAddWeighted( sigma1_sq, 1, mu1_sq, -1, 0, sigma1_sq );
cvSmooth( img2_sq, sigma2_sq, CV_GAUSSIAN, 11, 11, 1.5 );
cvAddWeighted( sigma2_sq, 1, mu2_sq, -1, 0, sigma2_sq );
cvSmooth( img1_img2, sigma12, CV_GAUSSIAN, 11, 11, 1.5 );
cvAddWeighted( sigma12, 1, mu1_mu2, -1, 0, sigma12 );
//////////////////////////////////////////////////////////////////////////
// FORMULA
// (2*mu1_mu2 + C1)
cvScale( mu1_mu2, temp1, 2 );
cvAddS( temp1, cvScalarAll(C1), temp1 );
// (2*sigma12 + C2)
cvScale( sigma12, temp2, 2 );
cvAddS( temp2, cvScalarAll(C2), temp2 );
// ((2*mu1_mu2 + C1).*(2*sigma12 + C2))
cvMul( temp1, temp2, temp3, 1 );
// (mu1_sq + mu2_sq + C1)
cvAdd( mu1_sq, mu2_sq, temp1 );
cvAddS( temp1, cvScalarAll(C1), temp1 );
// (sigma1_sq + sigma2_sq + C2)
cvAdd( sigma1_sq, sigma2_sq, temp2 );
cvAddS( temp2, cvScalarAll(C2), temp2 );
// ((mu1_sq + mu2_sq + C1).*(sigma1_sq + sigma2_sq + C2))
cvMul( temp1, temp2, temp1, 1 );
// ((2*mu1_mu2 + C1).*(2*sigma12 + C2))./((mu1_sq + mu2_sq + C1).*(sigma1_sq + sigma2_sq + C2))
cvDiv( temp3, temp1, ssim_map, 1 );
CvScalar index_scalar = cvAvg( ssim_map );
// through observation, there is approximately
// 1% error max with the original matlab program
cvReleaseImage(&img1);
cvReleaseImage(&img2);
cvReleaseImage(&ssim_map);
return index_scalar.val[0];
}