GRASS GIS 8 Programmer's Manual 8.2.0(2022)-exported
cairodriver/read_bmp.c
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1/*!
2 \file lib/cairodriver/read_bmp.c
3
4 \brief GRASS cairo display driver - read bitmap (lower level functions)
5
6 (C) 2007-2008 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 <stdio.h>
16#include <stdlib.h>
17#include <string.h>
18
19#include <grass/gis.h>
20#include <grass/glocale.h>
21#include "cairodriver.h"
22
23static unsigned int get_2(const unsigned char **q)
24{
25 const unsigned char *p = *q;
26 unsigned int n = (p[0] << 0) | (p[1] << 8);
27
28 *q += 2;
29 return n;
30}
31
32static unsigned int get_4(const unsigned char **q)
33{
34 const unsigned char *p = *q;
35 unsigned int n = (p[0] << 0) | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
36
37 *q += 4;
38 return n;
39}
40
41static int read_bmp_header(const unsigned char *p)
42{
43 if (*p++ != 'B')
44 return 0;
45 if (*p++ != 'M')
46 return 0;
47
48 if (get_4(&p) != HEADER_SIZE + ca.width * ca.height * 4)
49 return 0;
50
51 get_4(&p);
52
53 if (get_4(&p) != HEADER_SIZE)
54 return 0;
55
56 if (get_4(&p) != 40)
57 return 0;
58
59 if (get_4(&p) != ca.width)
60 return 0;
61 if (get_4(&p) != -ca.height)
62 return 0;
63
64 get_2(&p);
65 if (get_2(&p) != 32)
66 return 0;
67
68 if (get_4(&p) != 0)
69 return 0;
70 if (get_4(&p) != ca.width * ca.height * 4)
71 return 0;
72
73 get_4(&p);
74 get_4(&p);
75 get_4(&p);
76 get_4(&p);
77
78 return 1;
79}
80
82{
83 unsigned char header[HEADER_SIZE];
84 FILE *input;
85
86 input = fopen(ca.file_name, "rb");
87 if (!input)
88 G_fatal_error(_("Cairo: unable to open input file <%s>"),
90
91 if (fread(header, sizeof(header), 1, input) != 1)
92 G_fatal_error(_("Cairo: invalid input file <%s>"),
94
95 if (!read_bmp_header(header))
96 G_fatal_error(_("Cairo: Invalid BMP header for <%s>"),
98
99 fread(ca.grid, ca.stride, ca.height, input);
100
101 fclose(input);
102}
void cairo_read_bmp(void)
GRASS cairo display driver - header file.
#define HEADER_SIZE
Definition: cairodriver.h:45
struct cairo_state ca
void G_fatal_error(const char *msg,...)
Print a fatal error message to stderr.
Definition: gis/error.c:160
unsigned char * grid
Definition: cairodriver.h:68
char * file_name
Definition: cairodriver.h:65