Geografic-Information-System/lib/cairodriver/write_bmp.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <grass/gis.h>
#include "cairodriver.h"

static unsigned char *put_2(unsigned char *p, unsigned int n)
{
	*p++ = n & 0xFF;	n >>= 8;
	*p++ = n & 0xFF;
	return p;
}

static unsigned char *put_4(unsigned char *p, unsigned int n)
{
	*p++ = n & 0xFF;	n >>= 8;
	*p++ = n & 0xFF;	n >>= 8;
	*p++ = n & 0xFF;	n >>= 8;
	*p++ = n & 0xFF;
	return p;
}

static void make_bmp_header(unsigned char *p)
{
	*p++ = 'B';
	*p++ = 'M';

	p = put_4(p, HEADER_SIZE + width * height * 4);
	p = put_4(p, 0);
	p = put_4(p, HEADER_SIZE);

	p = put_4(p, 40);
	p = put_4(p, width);
	p = put_4(p, -height);
	p = put_2(p, 1);
	p = put_2(p, 32);
	p = put_4(p, 0);
	p = put_4(p, width * height * 4);
	p = put_4(p, 0);
	p = put_4(p, 0);
	p = put_4(p, 0);
	p = put_4(p, 0);
}

void write_bmp(void)
{
	char header[HEADER_SIZE];
	FILE *output;

	output = fopen(file_name, "wb");
	if (!output)
		G_fatal_error("cairo: couldn't open output file %s", file_name);

	make_bmp_header(header);
	fwrite(header, sizeof(header), 1, output);

	fwrite(grid, stride, height, output);

	fclose(output);
}