GRASS GIS 8 Programmer's Manual 8.2.1(2023)-exported
cairodriver/read_ppm.c
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1/*!
2 \file lib/cairodriver/read_ppm.c
3
4 \brief GRASS cairo display driver - read PPM image (lower level functions)
5
6 (C) 2007-2008, 2011 by Lars Ahlzen 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 Lars Ahlzen <lars ahlzen.com> (original contibutor)
12 \author Glynn Clements
13*/
14
15#include <grass/glocale.h>
16
17#include "cairodriver.h"
18
20{
21 char *mask_name = G_store(ca.file_name);
22 FILE *input, *mask;
23 int x, y;
24 int i_width, i_height, maxval;
25
26 input = fopen(ca.file_name, "rb");
27 if (!input)
28 G_fatal_error(_("Cairo: unable to open input file <%s>"),
30
31 if (fscanf(input, "P6 %d %d %d", &i_width, &i_height, &maxval) != 3)
32 G_fatal_error(_("Cairo: invalid input file <%s>"),
34
35 fgetc(input);
36
37 if (i_width != ca.width || i_height != ca.height)
38 G_fatal_error(_("Cairo: input file has incorrect dimensions: "
39 "expected: %dx%d got: %dx%d"),
40 ca.width, ca.height, i_width, i_height);
41
42 mask_name[strlen(mask_name) - 2] = 'g';
43
44 mask = fopen(mask_name, "rb");
45 if (!mask)
46 G_fatal_error(_("Cairo: unable to open input mask file <%s>"),
47 mask_name);
48
49 if (fscanf(mask, "P5 %d %d %d", &i_width, &i_height, &maxval) != 3)
50 G_fatal_error(_("Cairo: invalid input mask file <%s>"),
51 mask_name);
52
53 fgetc(mask);
54
55 if (i_width != ca.width || i_height != ca.height)
56 G_fatal_error(_("Cairo: input mask file has incorrect dimensions: "
57 "expected: %dx%d got: %dx%d"),
58 ca.width, ca.height, i_width, i_height);
59
60 G_free(mask_name);
61
62 for (y = 0; y < ca.height; y++) {
63 unsigned int *row = (unsigned int *)(ca.grid + y * ca.stride);
64
65 for (x = 0; x < ca.width; x++) {
66 int r = fgetc(input);
67 int g = fgetc(input);
68 int b = fgetc(input);
69 int a = fgetc(mask);
70
71 r = r * 255 / maxval;
72 g = g * 255 / maxval;
73 b = b * 255 / maxval;
74 a = a * 255 / maxval;
75
76 if (a > 0 && a < 0xFF) {
77 r = r * a / 0xFF;
78 g = g * a / 0xFF;
79 b = b * a / 0xFF;
80 }
81
82 row[x] = (a << 24) | (r << 16) | (g << 8) | (b << 0);
83 }
84 }
85
86 fclose(input);
87 fclose(mask);
88}
void G_free(void *buf)
Free allocated memory.
Definition: alloc.c:149
void cairo_read_ppm(void)
GRASS cairo display driver - header file.
struct cairo_state ca
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
char * G_store(const char *s)
Copy string to allocated memory.
Definition: strings.c:87
unsigned char * grid
Definition: cairodriver.h:68
char * file_name
Definition: cairodriver.h:65
#define x