GRASS GIS 8 Programmer's Manual  8.4.0dev(2024)-535c39c9fc
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 static void write_data(png_structp png_ptr, png_bytep data, png_size_t length)
24 {
25  png_size_t check;
26  FILE *fp;
27 
28  if (png_ptr == NULL)
29  return;
30 
31  fp = (FILE *)png_get_io_ptr(png_ptr);
32  if (fp == NULL)
33  return;
34 
35  check = fwrite(data, 1, length, fp);
36 
37  if (check != length)
38  G_fatal_error(_("Unable to write PNG"));
39 }
40 
41 static void output_flush(png_structp png_ptr)
42 {
43  FILE *fp;
44 
45  if (png_ptr == NULL)
46  return;
47 
48  fp = (FILE *)png_get_io_ptr(png_ptr);
49  if (fp == NULL)
50  return;
51 
52  fflush(fp);
53 }
54 
55 void write_png(void)
56 {
57  static jmp_buf jbuf;
58  static png_struct *png_ptr;
59  static png_info *info_ptr;
60  FILE *output;
61  int x, y;
62  unsigned int *p;
63  png_bytep line;
64  const char *str;
65  int compress;
66 
67  png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, &jbuf, NULL, NULL);
68  if (!png_ptr)
69  G_fatal_error(_("Unable to allocate PNG structure"));
70 
71  info_ptr = png_create_info_struct(png_ptr);
72  if (!info_ptr)
73  G_fatal_error(_("Unable to allocate PNG structure"));
74 
75  if (setjmp(png_jmpbuf(png_ptr)))
76  G_fatal_error(_("Unable to write PNG file"));
77 
78  output = fopen(png.file_name, "wb");
79  if (!output)
80  G_fatal_error(_("Unable to open output PNG file <%s>"), png.file_name);
81 
82  png_set_write_fn(png_ptr, output, write_data, output_flush);
83 
84  png_set_IHDR(png_ptr, info_ptr, png.width, png.height, 8,
85  png.true_color ? PNG_COLOR_TYPE_RGB_ALPHA
86  : PNG_COLOR_TYPE_PALETTE,
87  PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
88  PNG_FILTER_TYPE_DEFAULT);
89 
90  if (png.true_color)
91  png_set_invert_alpha(png_ptr);
92  else {
93  png_color png_pal[256];
94  int i;
95 
96  for (i = 0; i < 256; i++) {
97  png_pal[i].red = png.palette[i][0];
98  png_pal[i].green = png.palette[i][1];
99  png_pal[i].blue = png.palette[i][2];
100  }
101 
102  png_set_PLTE(png_ptr, info_ptr, png_pal, 256);
103 
104  if (png.has_alpha) {
105  png_byte trans = (png_byte)0;
106 
107  png_set_tRNS(png_ptr, info_ptr, &trans, 1, NULL);
108  }
109  }
110 
111  str = getenv("GRASS_RENDER_FILE_COMPRESSION");
112  if (str && sscanf(str, "%d", &compress) == 1)
113  png_set_compression_level(png_ptr, compress);
114 
115  png_write_info(png_ptr, info_ptr);
116 
117  line = G_malloc(png.width * 4);
118 
119  for (y = 0, p = png.grid; y < png.height; y++) {
120  png_bytep q = line;
121 
122  if (png.true_color)
123  for (x = 0; x < png.width; x++, p++) {
124  unsigned int c = *p;
125  int r, g, b, a;
126 
127  png_get_pixel(c, &r, &g, &b, &a);
128  *q++ = (png_byte)r;
129  *q++ = (png_byte)g;
130  *q++ = (png_byte)b;
131  *q++ = (png_byte)a;
132  }
133  else
134  for (x = 0; x < png.width; x++, p++, q++)
135  *q = (png_byte)*p;
136 
137  png_write_row(png_ptr, line);
138  }
139 
140  G_free(line);
141 
142  png_write_end(png_ptr, info_ptr);
143 
144  png_destroy_write_struct(&png_ptr, &info_ptr);
145 
146  fclose(output);
147 }
#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:110
void G_free(void *)
Free allocated memory.
Definition: gis/alloc.c:150
void void void void G_fatal_error(const char *,...) __attribute__((format(printf
#define G_malloc(n)
Definition: defs/gis.h:94
#define _(str)
Definition: glocale.h:10
float g
Definition: named_colr.c:7
struct png_state png
GRASS png display driver - header file.
void output(const char *fmt,...)
double b
Definition: r_raster.c:39
double r
Definition: r_raster.c:39
char * file_name
Definition: pngdriver.h:32
int has_alpha
Definition: pngdriver.h:35
int true_color
Definition: pngdriver.h:34
int height
Definition: pngdriver.h:42
unsigned int * grid
Definition: pngdriver.h:43
unsigned char palette[256][4]
Definition: pngdriver.h:44
int width
Definition: pngdriver.h:42
void write_png(void)
Definition: write_png.c:55
#define x