1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
|
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include "pngcp.h"
int
writeimage(const char *filename, png_uint_32 width, png_uint_32 height, int bitdepth, int channels,
png_byte *raster)
{
FILE *volatile image = NULL;
png_structp png = NULL;
png_infop info = NULL;
png_bytepp volatile row_pointers = NULL;
png_uint_32 i;
int rowbytes;
volatile int ret = -1;
int fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (fd < 0)
{
fprintf(stderr, "Could not open the output image\n");
goto cleanup;
}
if ((image = fdopen(fd, "wb")) == NULL)
{
fprintf(stderr, "Could not open the output image\n");
close(fd);
goto cleanup;
}
// Determine how many bytes each row will consume
rowbytes = bitdepth / 8;
if (bitdepth % 8 != 0)
rowbytes++;
rowbytes *= channels;
rowbytes *= width;
// Convert the raster into a series of row pointers
if ((row_pointers = malloc(height * sizeof(png_bytep))) == NULL)
{
fprintf(stderr, "Could not allocate memory\n");
goto cleanup;
}
for (i = 0; i < height; ++i)
row_pointers[i] = raster + (i * rowbytes);
// Get ready for writing
if ((png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL)) == NULL)
{
fprintf(stderr, "Could not create write structure for PNG (out of memory?)\n");
goto cleanup;
}
// The pixels are expanded to the nearest byte
png_set_expand(png);
// Get ready to specify important stuff about the image
if ((info = png_create_info_struct(png)) == NULL)
{
fprintf(stderr, "Could not create PNG info structure for writing (out of memory?)\n");
goto cleanup;
}
if (setjmp(png_jmpbuf(png)))
{
fprintf(stderr, "Could not set the PNG jump value for writing\n");
goto cleanup;
}
// This is needed before IO will work (unless you define callbacks)
png_init_io(png, image);
// Derive the PNG color type from the number of channels
int colourtype;
switch (channels)
{
case 1:
colourtype = PNG_COLOR_TYPE_GRAY;
break;
case 2:
colourtype = PNG_COLOR_TYPE_GRAY_ALPHA;
break;
case 3:
colourtype = PNG_COLOR_TYPE_RGB;
break;
case 4:
colourtype = PNG_COLOR_TYPE_RGB_ALPHA;
break;
default:
fprintf(stderr, "Unsupported channel count: %d\n", channels);
goto cleanup;
}
// Define important stuff about the image
png_set_IHDR(png, info, width, height, bitdepth, colourtype, PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
png_write_info(png, info);
// Write the image out
png_write_image(png, row_pointers);
// Success
png_write_end(png, info);
ret = 0;
cleanup:
if (png != NULL)
png_destroy_write_struct(&png, &info);
free(row_pointers);
if (image != NULL)
fclose(image);
return ret;
}
|
