GRASS GIS 8 Programmer's Manual  8.5.0dev(2025)-56109d36f5
pngdriver/read_ppm.c
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1 /*!
2  \file lib/pngdriver/read_ppm.c
3 
4  \brief GRASS png display driver - read 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 <string.h>
17 
18 #include <grass/gis.h>
19 #include <grass/glocale.h>
20 #include "pngdriver.h"
21 
22 void read_ppm(void)
23 {
24  FILE *input;
25  int x, y;
26  int i_width, i_height, maxval;
27  unsigned int rgb_mask = png_get_color(255, 255, 255, 0);
28  unsigned int *p;
29 
30  if (!png.true_color)
31  G_fatal_error("PNG: cannot use PPM/PGM with indexed color");
32 
33  input = fopen(png.file_name, "rb");
34  if (!input)
35  G_fatal_error("PNG: couldn't open input file %s", png.file_name);
36 
37  if (fscanf(input, "P6 %d %d %d", &i_width, &i_height, &maxval) != 3)
38  G_fatal_error("PNG: invalid input file %s", png.file_name);
39 
40  if (fgetc(input) == EOF)
41  G_fatal_error(_("PNG: invalid input file %s"), png.file_name);
42 
43  if (i_width != png.width || i_height != png.height)
44  G_fatal_error("PNG: input file has incorrect dimensions: expected: "
45  "%dx%d got: %dx%d",
46  png.width, png.height, i_width, i_height);
47 
48  for (y = 0, p = png.grid; y < png.height; y++) {
49  for (x = 0; x < png.width; x++, p++) {
50  unsigned int c = *p;
51 
52  int r = fgetc(input);
53  int g = fgetc(input);
54  int b = fgetc(input);
55 
56  r = r * 255 / maxval;
57  g = g * 255 / maxval;
58  b = b * 255 / maxval;
59 
60  c &= ~rgb_mask;
61  c |= png_get_color(r, g, b, 0);
62 
63  *p = c;
64  }
65  }
66 
67  fclose(input);
68 }
69 
70 void read_pgm(void)
71 {
72  char *mask_name = G_store(png.file_name);
73  FILE *input;
74  int x, y;
75  int i_width, i_height, maxval;
76  unsigned int rgb_mask = png_get_color(255, 255, 255, 0);
77  unsigned int *p;
78 
79  if (!png.true_color)
80  G_fatal_error("PNG: cannot use PPM/PGM with indexed color");
81 
82  mask_name[strlen(mask_name) - 2] = 'g';
83 
84  input = fopen(mask_name, "rb");
85  if (!input)
86  G_fatal_error("PNG: couldn't open input mask file %s", mask_name);
87 
88  if (fscanf(input, "P5 %d %d %d", &i_width, &i_height, &maxval) != 3)
89  G_fatal_error("PNG: invalid input mask file %s", mask_name);
90 
91  if (fgetc(input) == EOF)
92  G_fatal_error(_("PNG: invalid input mask file %s"), mask_name);
93 
94  if (i_width != png.width || i_height != png.height)
95  G_fatal_error("PNG: input mask file has incorrect dimensions: "
96  "expected: %dx%d got: %dx%d",
97  png.width, png.height, i_width, i_height);
98 
99  G_free(mask_name);
100 
101  for (y = 0, p = png.grid; y < png.height; y++) {
102  for (x = 0; x < png.width; x++, p++) {
103  unsigned int c = *p;
104 
105  int k = fgetc(input);
106 
107  k = k * 255 / maxval;
108 
109  c &= rgb_mask;
110  c |= png_get_color(0, 0, 0, 255 - k);
111 
112  *p = c;
113  }
114  }
115 
116  fclose(input);
117 }
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
char * G_store(const char *)
Copy string to allocated memory.
Definition: strings.c:87
#define _(str)
Definition: glocale.h:10
float g
Definition: named_colr.c:7
struct png_state png
void read_ppm(void)
void read_pgm(void)
GRASS png display driver - header file.
double b
Definition: r_raster.c:39
double r
Definition: r_raster.c:39
char * file_name
Definition: pngdriver.h:32
int true_color
Definition: pngdriver.h:34
int height
Definition: pngdriver.h:42
unsigned int * grid
Definition: pngdriver.h:43
int width
Definition: pngdriver.h:42
#define x