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/*
* pnmpsnr.c: Compute error (RMSE, PSNR) between images
*
*
* Derived from pnmpnsmr by Ulrich Hafner, part of his fiasco package,
* On 2001.03.04.
* Copyright (C) 1994-2000 Ullrich Hafner <hafner@bigfoot.de>
*/
#include <string.h>
#include <stdio.h>
#include <math.h>
#include "pm_c_util.h"
#include "nstring.h"
#include "pam.h"
#define MAXFILES 16
static int
udiff(unsigned int const subtrahend, unsigned int const subtractor) {
return subtrahend-subtractor;
}
static double
square(double const arg) {
return(arg*arg);
}
static void
validate_input(const struct pam pam1, const struct pam pam2) {
if (pam1.width != pam2.width)
pm_error("images are not the same width, so can't be compared. "
"The first is %d columns wide, "
"while the second is %d columns wide.",
pam1.width, pam2.width);
if (pam1.height != pam2.height)
pm_error("images are not the same height, so can't be compared. "
"The first is %d rows high, "
"while the second is %d rows high.",
pam1.height, pam2.height);
if (pam1.maxval != pam2.maxval)
pm_error("images do not have the same maxval. This programs works "
"only on like maxvals. "
"The first image has maxval %u, "
"while the second has %u. Use Pamdepth to change the "
"maxval of one of them.",
(unsigned int) pam1.maxval, (unsigned int) pam2.maxval);
if (strcmp(pam1.tuple_type, pam2.tuple_type) != 0)
pm_error("images are not of the same type. The tuple types are "
"'%s' and '%s', respectively.",
pam1.tuple_type, pam2.tuple_type);
if (strcmp(pam1.tuple_type, PAM_PBM_TUPLETYPE) != 0 &&
strcmp(pam1.tuple_type, PAM_PGM_TUPLETYPE) != 0 &&
strcmp(pam1.tuple_type, PAM_PPM_TUPLETYPE) != 0)
pm_error("Images are not of a PNM type. Tuple type is '%s'",
pam1.tuple_type);
}
static void
psnr_color(tuple const tuple1,
tuple const tuple2,
double * const ySqDiffP,
double * const cbSqDiffP,
double * const crSqDiffP) {
double y1, y2, cb1, cb2, cr1, cr2;
pnm_YCbCrtuple(tuple1, &y1, &cb1, &cr1);
pnm_YCbCrtuple(tuple2, &y2, &cb2, &cr2);
*ySqDiffP = square(y1 - y2);
*cbSqDiffP = square(cb1 - cb2);
*crSqDiffP = square(cr1 - cr2);
}
static void
reportPsnr(struct pam const pam,
double const ySumSqDiff,
double const crSumSqDiff,
double const cbSumSqDiff,
char const filespec1[],
char const filespec2[]) {
bool const color = streq(pam.tuple_type, PAM_PPM_TUPLETYPE);
/* The PSNR is the ratio of the maximum possible mean square difference
to the actual mean square difference.
*/
double const yPsnr =
square(pam.maxval) / (ySumSqDiff / (pam.width * pam.height));
/* Note that in the important special case that the images are
identical, the sum square differences are identically 0.0. No
precision error; no rounding error.
*/
if (color) {
double const cbPsnr =
square(pam.maxval) / (cbSumSqDiff / (pam.width * pam.height));
double const crPsnr =
square(pam.maxval) / (crSumSqDiff / (pam.width * pam.height));
pm_message("PSNR between %s and %s:", filespec1, filespec2);
if (ySumSqDiff > 0)
pm_message("Y color component: %.2f dB", 10 * log10(yPsnr));
else
pm_message("Y color component does not differ.");
if (cbSumSqDiff > 0)
pm_message("Cb color component: %.2f dB", 10 * log10(cbPsnr));
else
pm_message("Cb color component does not differ.");
if (crSumSqDiff > 0)
pm_message("Cr color component: %.2f dB", 10 * log10(crPsnr));
else
pm_message("Cr color component does not differ.");
} else {
if (ySumSqDiff > 0)
pm_message("PSNR between %s and %s: %.2f dB",
filespec1, filespec2, 10 * log10(yPsnr));
else
pm_message("Images %s and %s don't differ.",
filespec1, filespec2);
}
}
int
main (int argc, char **argv) {
char *filespec1, *filespec2; /* specs of two files to compare */
FILE *file1, *file2;
struct pam pam1, pam2;
bool color;
/* It's a color image */
double ySumSqDiff, crSumSqDiff, cbSumSqDiff;
tuple *tuplerow1, *tuplerow2; /* malloc'ed */
int row;
pnm_init(&argc, argv);
if (argc-1 < 2)
pm_error("Takes two arguments: specifications of the two files.");
else {
filespec1 = argv[1];
filespec2 = argv[2];
}
file1 = pm_openr(filespec1);
file2 = pm_openr(filespec2);
pnm_readpaminit(file1, &pam1, PAM_STRUCT_SIZE(tuple_type));
pnm_readpaminit(file2, &pam2, PAM_STRUCT_SIZE(tuple_type));
validate_input(pam1, pam2);
if (strcmp(pam1.tuple_type, PAM_PPM_TUPLETYPE) == 0)
color = TRUE;
else
color = FALSE;
tuplerow1 = pnm_allocpamrow(&pam1);
tuplerow2 = pnm_allocpamrow(&pam2);
ySumSqDiff = 0.0;
cbSumSqDiff = 0.0;
crSumSqDiff = 0.0;
for (row = 0; row < pam1.height; ++row) {
int col;
pnm_readpamrow(&pam1, tuplerow1);
pnm_readpamrow(&pam2, tuplerow2);
for (col = 0; col < pam1.width; ++col) {
if (color) {
double ySqDiff, cbSqDiff, crSqDiff;
psnr_color(tuplerow1[col], tuplerow2[col],
&ySqDiff, &cbSqDiff, &crSqDiff);
ySumSqDiff += ySqDiff;
cbSumSqDiff += cbSqDiff;
crSumSqDiff += crSqDiff;
} else {
unsigned int const yDiffSq =
square(udiff(tuplerow1[col][0], tuplerow2[col][0]));
ySumSqDiff += yDiffSq;
}
}
}
reportPsnr(pam1, ySumSqDiff, crSumSqDiff, cbSumSqDiff,
filespec1, filespec2);
pnm_freepamrow(tuplerow1);
pnm_freepamrow(tuplerow2);
return 0;
}
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