## NAME

         snr - computes the rms error between two images

## SYNOPSIS

          #include <CVIPimage.h>
          #include "CVIPcompress.h"

         float *snr(Image *im1, Image *im2)

          <im1> - Pointer to Image
          <im2> - Pointer to Image

          RETURNS: Pointer to rms values (float)

## PATH

         $CVIPHOME/COMPRESSION/rms_error.c

## DESCRIPTION

         snr() calculates the Peak Signal-to-Noise ratio between  two
         images, assuming a maximum value of 255 (BYTE).

         The number of values contained in the return value of  snr()
         is  equal  to bands+1.  Thus, for a color image (RGB), snr()
         will return float *fptr;  where  fptr[0]=snr  in  Red  Band;
         fptr[1]=snr  in  Green  band;  fptr[2]=snr in Blue band; and
         fptr[3] is overall SNR.

         If case if there is no error between two images for a  band,
         the  return value for that band is set to -1.0 as an indica-
         tion.

         The input images may be any data type, but for the result to
         be meaningful the maximum value should be around 255.

## EXAMPLE

          #include <CVIPimage.h>
          #include <CVIPhisto.h>

          void main()
          {
          Image *cvipImage, *heqimage;
          IMAGE_FORMAT format;
          char *inputfile;
          float *error;
          int i;

          print_CVIP("\n\t\tEnter the Input File Name:  ");
          inputfile =(char *) getString_CVIP();
          format = getFormat_CVIP(inputfile);
          cvipImage = read_Image(inputfile, 1);
          heqimage=histeq(cvipImage);
          error = snr(cvipImage, heqimage);
          for(i=0; i<getNoOfBands_Image(cvipImage); i++) {
             fprintf(stdout, "SNR in band #%d: %f0, i, error[i]);
          }
          fprintf(stdout,         "Overall         SNR:          %f0,
         error[getNoOfBands_Image(cvipImage)];

## BUGS

         None at this time

## SEE ALSO

         snr()

## AUTHOR

         Copyright (C) 1993-1996 SIUE - by  Scott  Umbaugh  and  Arve
         Kjoelen