fpsnr255.c

image processing including fourier,wavelet,segmentation etc.

/*--------------------------- Commande MegaWave -----------------------------*/
/* mwcommand
name = {fpsnr255};
author = {"Jacques Froment"};
function = {"Returns the additive factor to get the '255' PSNR from the 'max-min' PSNR"};
version = {"0.0"};
usage = {
'n'->Norm     "flag to normalize the image",
Image->image    "original image", 
ADDPSNR<-fpsnr255 "additive PSNR factor"
};
 */

/*--- Fichiers inclus UNIX C ---*/
#include <stdio.h>
#include <math.h>

/*--- Bibliotheque megawave2 ---*/
#include  "mw.h"

void
NORM_IMG(image)

	/*--- Normalize `image` to 0.0 mean and 1.0 variance ---*/

    Fimage	image;

{
    long	l, c;		/* Index of current point in `image` */
    long	dx, dy;		/* Size of image */
    double	mean, var;	/* Mean and variance of `image` */

    dx = image->ncol;
    dy = image->nrow;

    mean = 0.0;
    for(l = 0; l < dy; l++)
	for(c = 0; c < dx; c++)
	    mean += image->gray[dx * l + c];
    mean /= (double) dx * dy;
    for(l = 0; l < dy; l++)
	for(c = 0; c < dx; c++)
	    image->gray[dx * l + c] -= mean;

    var = 0.0;
    for(l = 0; l < dy; l++)
	for(c = 0; c < dx; c++)
	    var += image->gray[dx * l + c] * image->gray[dx * l + c];
    var = sqrt(((double) dx * dy - 1.0) / var);
    for(l = 0; l < dy; l++)
	for(c = 0; c < dx; c++)
	    image->gray[dx * l + c] *= var;

}

double fpsnr255(Norm,image)

    Fimage	image;
    int		*Norm;		/* Normalisation to 0 mean and 1.0 variance */
{
    long	l, c;		/* Index of current point in image */
    long	ldx;
    long	dx, dy;		/* Size of image */
    double	min, max;	/* Minimum and maximum of `image` values */

    dx = image->ncol;
    dy = image->nrow;

    if(Norm) NORM_IMG(image);

    min = 1e30;
    max = -min;

    ldx =0;
    for(l = 0; l < dy; l++)
      {
	for(c = 0; c < dx; c++)
	  {
	    if(image->gray[ldx + c] < min) min = image->gray[ldx + c];
	    if(image->gray[ldx + c] > max) max = image->gray[ldx + c];
	  }
	ldx += dx;
      }

    return(10.0 * log10((255.0*255.0)/((max - min)* (max - min))) );
}