« back to all changes in this revision
Viewing changes to 0.4.1/pngcomp.c
- browse files at revision 3
- compare with another revision
- download diff
- download tarball
- view history from revision 3
- Committer: Bazaar Package Importer
- Author(s): Nelson A. de Oliveira
- Date: 2006-07-15 00:24:51 UTC
- mfrom: (1.1.1 upstream) (2.1.1 edgy)
- Revision ID: james.westby@ubuntu.com-20060715002451-bbdi09ckv5rn0e7g
Tags: 0.4.1-1
New upstream release (Closes: #378148).
- files added:
- 0.4.1
- files removed:
- LICENSE
- files modified:
- debian/changelog
added
removed
0.4.1/pngcomp.c
1
/* pngcomp.c
2
3
A simple test program for png image quantisation.
4
5
This program compares the pixel colors of two images and prints out
6
statistics on the differences between the images.
7
8
Statistics printed include:
9
mean error
10
standard deviation of error
11
maximum error
12
13
The error is calculated as the linear distance between two colors in RGBA space.
14
15
Copyright (C) 2006 by Stuart Coyle
16
17
*/
18
#define VERSION "0.1"
19
#define PNGCOMP_USAGE "usage: pngcomp [-vVh] image1.png image2.png\n\
20
options: v - verbose, does nothing as yet.\n\
21
V - version, prints version information.\n\
22
h - help, prionts this message.\n\
23
inputs: image1.png and image2.png are the two images that are to be compared.\n\
24
it is required that they be the same size.\n\
25
\n\
26
This program give some basic statistics about the difference between two images.\n\
27
It was created as a measure of various color quantization methods.\n"
28
29
#define MAX_COLOR_VAL 256
30
#define SQRT_3 1.73205
31
32
#include <stdlib.h>
33
#include <stdio.h>
34
#include <string.h>
35
#include <unistd.h>
36
#include <math.h>
37
#include <ctype.h>
38
39
#include "png.h"
40
#include "rwpng.h"
41
42
typedef struct {
43
uch r, g, b, a;
44
} pixel;
45
46
struct statistics {
47
double max_error;
48
double mean_error;
49
double stddev_error;
50
ulg n_pixels;
51
ulg correct_pixels;
52
};
53
54
/* Image information structs */
55
static mainprog_info image1_info;
56
static mainprog_info image2_info;
57
58
float *imagediff(char* file1_name, char* file2_name);
59
float errval(pixel *p1, pixel *p2);
60
struct statistics *gather_stats(float *error_data);
61
void printstats(struct statistics* stats);
62
63
64
int main(int argc, char** argv)
65
{
66
int verbose = 0;
67
68
char *file1_name = NULL;
69
char *file2_name = NULL;
70
71
int c; /* argument count */
72
73
int retval = 0;
74
float* err_image = NULL;
75
76
/* Parse arguments */
77
while((c = getopt(argc,argv,"hVv"))!=-1){
78
switch(c){
79
case 'v':
80
verbose = 1;
81
break;
82
case 'V':
83
fprintf(stderr,"pngcomp %s\n",VERSION);
84
rwpng_version_info();
85
exit(EXIT_SUCCESS);
86
break;
87
case 'h':
88
fprintf(stderr,PNGCOMP_USAGE);
89
exit(EXIT_SUCCESS);
90
break;
91
case '?':
92
if (isprint(optopt))
93
fprintf (stderr, " unknown option `-%c'.\n", optopt);
94
else
95
fprintf (stderr,
96
" unknown option character `\\x%x'.\n",
97
optopt);
98
default:
99
fprintf(stderr,PNGCOMP_USAGE);
100
exit(EXIT_FAILURE);
101
}
102
}
103
104
105
/* determine input files */
106
if(optind == argc){
107
fprintf(stderr," pngcomp requires two input file names.\n");
108
exit(EXIT_FAILURE);
109
}
110
else{
111
file1_name=argv[optind];
112
optind++;
113
if(optind == argc){
114
fprintf(stderr," pngcomp requires two file names.\n");
115
exit(EXIT_FAILURE);
116
}
117
else{
118
file2_name=argv[optind];
119
optind++;
120
}
121
}
122
123
err_image = imagediff(file1_name,file2_name);
124
if(err_image != NULL){
125
struct statistics *stats = gather_stats(err_image);
126
printstats(stats);
127
}
128
129
exit(retval);
130
131
}
132
133
134
float *imagediff(char* file1_name, char* file2_name){
135
136
FILE *file1 = NULL;
137
FILE *file2 = NULL;
138
139
ulg cols, rows;
140
ulg row;
141
142
float* error_data = NULL;
143
144
/* Open the image files */
145
if((file1 = fopen(file1_name, "rb"))==NULL){
146
fprintf(stderr," error: cannot open %s for reading.\n",file1_name);
147
fflush(stderr);
148
return NULL;
149
}
150
151
if((file2 = fopen(file2_name, "rb"))==NULL){
152
fprintf(stderr," error: cannot open %s for reading.\n",file2_name);
153
fflush(stderr);
154
return NULL;
155
}
156
157
/* Read each image */
158
rwpng_read_image(file1,&image1_info);
159
fclose(file1);
160
if (image1_info.retval) {
161
fprintf(stderr, " rwpng_read_image() error\n");
162
fflush(stderr);
163
return NULL;
164
}
165
166
rwpng_read_image(file2,&image2_info);
167
fclose(file2);
168
if (image2_info.retval) {
169
fprintf(stderr, " rwpng_read_image() error\n");
170
fflush(stderr);
171
return NULL;
172
}
173
174
/* Can't do images that differ in size */
175
/* Is there any point? */
176
cols = image1_info.width;
177
rows= image1_info.height;
178
179
if(image2_info.width != cols || image2_info.height != rows){
180
fprintf(stderr, " images differ in size. cannot continue. \n");
181
return(NULL);
182
}
183
184
185
if(!image1_info.rgba_data || !image2_info.rgba_data)
186
{
187
fprintf(stderr," no pixel data found.");
188
return(NULL);
189
}
190
191
error_data = (float *)calloc(cols*rows*sizeof(float),sizeof(float));
192
if(error_data == NULL){
193
fprintf(stderr," cannot allocate error buffer.");
194
return(NULL);
195
}
196
197
198
/* Calculate error value for each pixel */
199
for(row=0;(ulg)row < rows; ++row){
200
int col;
201
pixel p1, p2;
202
ulg offset = row*cols*4;
203
204
for( col=0;(ulg)col<cols;++col){
205
p1.r = image1_info.rgba_data[col*4+offset];
206
p1.g = image1_info.rgba_data[col*4+offset+1];
207
p1.b = image1_info.rgba_data[col*4+offset+2];
208
p1.a = image1_info.rgba_data[col*4+offset+3];
209
210
p2.r = image2_info.rgba_data[col*4+offset];
211
p2.g = image2_info.rgba_data[col*4+offset+1];
212
p2.b = image2_info.rgba_data[col*4+offset+2];
213
p2.a = image2_info.rgba_data[col*4+offset+3];
214
215
error_data[col*row] = errval(&p1,&p2);
216
217
}
218
}
219
return error_data;
220
}
221
222
223
/* Calculates cartesian distance of pixels in rgba space */
224
float errval(pixel *p1, pixel *p2){
225
long err;
226
227
long err_r = p1->r-p2->r;
228
long err_g = p1->g-p2->g;
229
long err_b = p1->b-p2->b;
230
long err_a = p1->a-p2->a;
231
err = err_r*err_r + err_g*err_g + err_b*err_b+ err_a*err_a;
232
return sqrt((double)err);
233
}
234
235
236
struct statistics *gather_stats(float *error_data){
237
238
int count;
239
struct statistics *stats = malloc(sizeof(struct statistics));
240
241
if(stats == NULL){
242
fprintf(stderr," Cannot allocate statistics struct.");
243
return(NULL);
244
}
245
246
247
stats->max_error = 0.0;
248
stats->mean_error = 0.0;
249
stats->stddev_error = 0.0;
250
stats->n_pixels = image1_info.width*image1_info.height;
251
stats->correct_pixels = (ulg)0;
252
253
/* Basic stats */
254
for(count=0;count<stats->n_pixels;count++){
255
float err = error_data[count];
256
if(err > stats->max_error) stats->max_error = err;
257
stats->mean_error += err;
258
if(err <= 0.0) stats->correct_pixels++;
259
}
260
stats->mean_error = (float)(stats->mean_error)/(float)(stats->n_pixels);
261
262
/* Standard deviation */
263
for(count=0;count<stats->n_pixels;count++){
264
double err= error_data[count];
265
stats->stddev_error += (err-stats->mean_error)*(err-stats->mean_error);
266
}
267
stats->stddev_error = sqrt(stats->stddev_error)/stats->n_pixels;
268
269
return stats;
270
271
}
272
273
274
void printstats(struct statistics* stats){
275
printf("RGBA image color difference statistics.\n");
276
printf("Mean error: %f \n",stats->mean_error);
277
printf("Maximum error: %f \n",stats->max_error);
278
printf("Standard Deviation of Error: %f\n",stats->stddev_error);
279
printf("Image Dimensions %d x %d \n",image1_info.width,image1_info.height);
280
printf("Number of pixels: %d \n",stats->n_pixels);
281
printf("Number of correct pixels: %d\n",stats->correct_pixels);
282
printf("Percentage correct pixels: %f%\n",(float)stats->correct_pixels/(float)stats->n_pixels*100.0);
283
284
}
285
Loggerhead is a web-based interface for Breezy
Version: 2.0.1