GRASS GIS 8 Programmer's Manual  8.4.0dev(2024)-6da4f45b8e
read_png.c
Go to the documentation of this file.
1 /*!
2  \file lib/pngdriver/read_png.c
3 
4  \brief GRASS png display driver - read png
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 read_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 
33  if (fp == NULL)
34  return;
35 
36  /* fread() returns 0 on error, so it is OK to store this in a png_size_t
37  * instead of an int, which is what fread() actually returns.
38  */
39  check = fread(data, 1, length, fp);
40 
41  if (check != length)
42  G_fatal_error(_("Unable to read PNG"));
43 }
44 
45 void read_png(void)
46 {
47  static jmp_buf jbuf;
48  static png_struct *png_ptr;
49  static png_info *info_ptr;
50  FILE *input;
51  int x, y;
52  unsigned int *p;
53  png_bytep line;
54  png_uint_32 i_width, i_height;
55  int depth, color_type;
56 
57  png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, &jbuf, NULL, NULL);
58  if (!png_ptr)
59  G_fatal_error(_("Unable to allocate PNG structure"));
60 
61  info_ptr = png_create_info_struct(png_ptr);
62  if (!info_ptr)
63  G_fatal_error(_("Unable to allocate PNG structure"));
64 
65  if (setjmp(png_jmpbuf(png_ptr)))
66  G_fatal_error(_("Unable to read PNG file"));
67 
68  input = fopen(png.file_name, "rb");
69  if (!input)
70  G_fatal_error(_("Unable to open output file <%s>"), png.file_name);
71 
72  png_set_read_fn(png_ptr, input, read_data);
73 
74  png_read_info(png_ptr, info_ptr);
75 
76  png_get_IHDR(png_ptr, info_ptr, &i_width, &i_height, &depth, &color_type,
77  NULL, NULL, NULL);
78 
79  if (depth != 8)
80  G_fatal_error(_("Input PNG file is not 8-bit"));
81 
82  if (i_width != (unsigned long)png.width ||
83  i_height != (unsigned long)png.height)
84  G_fatal_error(_("Input PNG file has incorrect dimensions: expected: "
85  "%dx%d got: %lux%lu"),
86  png.width, png.height, (unsigned long)i_width,
87  (unsigned long)i_height);
88 
89  if (png.true_color) {
90  if (color_type != PNG_COLOR_TYPE_RGB_ALPHA)
91  G_fatal_error(_("Input PNG file is not RGBA"));
92  }
93  else {
94  if (color_type != PNG_COLOR_TYPE_PALETTE)
95  G_fatal_error(_("Input PNG file is not indexed color"));
96  }
97 
98  if (!png.true_color && png.has_alpha) {
99  png_bytep trans;
100  int num_trans;
101 
102  png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, NULL);
103 
104  if (num_trans != 1 || trans[0] != 0)
105  G_fatal_error(_("Input PNG file has invalid palette"));
106  }
107 
108  if (png.true_color)
109  png_set_invert_alpha(png_ptr);
110  else {
111  png_colorp png_pal;
112  int num_palette;
113  int i;
114 
115  png_get_PLTE(png_ptr, info_ptr, &png_pal, &num_palette);
116 
117  if (num_palette > 256)
118  num_palette = 256;
119 
120  for (i = 0; i < num_palette; i++) {
121  png.palette[i][0] = png_pal[i].red;
122  png.palette[i][1] = png_pal[i].green;
123  png.palette[i][2] = png_pal[i].blue;
124  }
125  }
126 
127  line = G_malloc(png.width * 4);
128 
129  for (y = 0, p = png.grid; y < png.height; y++) {
130  png_bytep q = line;
131 
132  png_read_row(png_ptr, q, NULL);
133 
134  if (png.true_color)
135  for (x = 0; x < png.width; x++, p++) {
136  int r = *q++;
137  int g = *q++;
138  int b = *q++;
139  int a = *q++;
140  unsigned int c = png_get_color(r, g, b, a);
141 
142  *p = c;
143  }
144  else
145  for (x = 0; x < png.width; x++, p++, q++)
146  *p = (png_byte)*q;
147  }
148 
149  G_free(line);
150 
151  png_read_end(png_ptr, NULL);
152 
153  png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
154 
155  fclose(input);
156 }
#define NULL
Definition: ccmath.h:32
unsigned int png_get_color(int r, int g, int b, int a)
Definition: color_table.c:118
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.
double b
Definition: r_raster.c:39
double r
Definition: r_raster.c:39
void read_png(void)
Definition: read_png.c:45
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
#define x