GRASS GIS 8 Programmer's Manual 8.2.1RC1(2022)-exported
write_png.c
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1/*!
2 \file lib/pngdriver/write_png.c
3
4 \brief GRASS png display driver - write PPM image (lower level functions)
5
6 (C) 2007-2014 by Glynn Clements and the GRASS Development Team
7
8 This program is free software under the GNU General Public License
9 (>=v2). Read the file COPYING that comes with GRASS for details.
10
11 \author Glynn Clements
12*/
13
14#include <stdio.h>
15#include <stdlib.h>
16#include <png.h>
17
18#include <grass/gis.h>
19#include <grass/glocale.h>
20
21#include "pngdriver.h"
22
23
24static void write_data(png_structp png_ptr, png_bytep data, png_size_t length)
25{
26 png_size_t check;
27 FILE *fp;
28
29 if (png_ptr == NULL )
30 return;
31
32 fp = (FILE *) png_get_io_ptr(png_ptr);
33 if ( fp == NULL )
34 return;
35
36 check = fwrite(data, 1, length, fp);
37
38 if (check != length)
39 G_fatal_error(_("Unable to write PNG"));
40}
41
42static void output_flush(png_structp png_ptr)
43{
44 FILE *fp;
45
46 if (png_ptr == NULL )
47 return;
48
49 fp = (FILE *) png_get_io_ptr(png_ptr);
50 if ( fp == NULL )
51 return;
52
53 fflush( fp );
54}
55
56void write_png(void)
57{
58 static jmp_buf jbuf;
59 static png_struct *png_ptr;
60 static png_info *info_ptr;
61 FILE *output;
62 int x, y;
63 unsigned int *p;
64 png_bytep line;
65 const char *str;
66 int compress;
67
68 png_ptr =
69 png_create_write_struct(PNG_LIBPNG_VER_STRING, &jbuf, NULL, NULL);
70 if (!png_ptr)
71 G_fatal_error(_("Unable to allocate PNG structure"));
72
73 info_ptr = png_create_info_struct(png_ptr);
74 if (!info_ptr)
75 G_fatal_error(_("Unable to allocate PNG structure"));
76
77 if (setjmp(png_jmpbuf(png_ptr)))
78 G_fatal_error(_("Unable to write PNG file"));
79
80 output = fopen(png.file_name, "wb");
81 if (!output)
82 G_fatal_error(_("Unable to open output PNG file <%s>"), png.file_name);
83
84 png_set_write_fn(png_ptr, output, write_data, output_flush);
85
86 png_set_IHDR(png_ptr, info_ptr,
87 png.width, png.height, 8,
88 png.true_color ? PNG_COLOR_TYPE_RGB_ALPHA :
89 PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
90 PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
91
92 if (png.true_color)
93 png_set_invert_alpha(png_ptr);
94 else {
95 png_color png_pal[256];
96 int i;
97
98 for (i = 0; i < 256; i++) {
99 png_pal[i].red = png.palette[i][0];
100 png_pal[i].green = png.palette[i][1];
101 png_pal[i].blue = png.palette[i][2];
102 }
103
104 png_set_PLTE(png_ptr, info_ptr, png_pal, 256);
105
106 if (png.has_alpha) {
107 png_byte trans = (png_byte) 0;
108
109 png_set_tRNS(png_ptr, info_ptr, &trans, 1, NULL);
110 }
111 }
112
113 str = getenv("GRASS_RENDER_FILE_COMPRESSION");
114 if (str && sscanf(str, "%d", &compress) == 1)
115 png_set_compression_level(png_ptr, compress);
116
117 png_write_info(png_ptr, info_ptr);
118
119 line = G_malloc(png.width * 4);
120
121 for (y = 0, p = png.grid; y < png.height; y++) {
122 png_bytep q = line;
123
124 if (png.true_color)
125 for (x = 0; x < png.width; x++, p++) {
126 unsigned int c = *p;
127 int r, g, b, a;
128
129 png_get_pixel(c, &r, &g, &b, &a);
130 *q++ = (png_byte) r;
131 *q++ = (png_byte) g;
132 *q++ = (png_byte) b;
133 *q++ = (png_byte) a;
134 }
135 else
136 for (x = 0; x < png.width; x++, p++, q++)
137 *q = (png_byte) * p;
138
139 png_write_row(png_ptr, line);
140 }
141
142 G_free(line);
143
144 png_write_end(png_ptr, info_ptr);
145
146 png_destroy_write_struct(&png_ptr, &info_ptr);
147
148 fclose(output);
149}
void G_free(void *buf)
Free allocated memory.
Definition: alloc.c:149
#define NULL
Definition: ccmath.h:32
void png_get_pixel(unsigned int pixel, int *r, int *g, int *b, int *a)
Definition: color_table.c:112
double b
double r
void G_fatal_error(const char *msg,...)
Print a fatal error message to stderr.
Definition: gis/error.c:160
float g
Definition: named_colr.c:8
struct png_state png
GRASS png display driver - header file.
void output(const char *fmt,...)
char * file_name
Definition: pngdriver.h:33
int has_alpha
Definition: pngdriver.h:36
int true_color
Definition: pngdriver.h:35
int height
Definition: pngdriver.h:43
unsigned int * grid
Definition: pngdriver.h:44
unsigned char palette[256][4]
Definition: pngdriver.h:45
int width
Definition: pngdriver.h:43
void write_png(void)
Definition: write_png.c:56
#define x