cairodriver/write_bmp.c

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/*!
   \file lib/cairodriver/write_bmp.c
 
   \brief GRASS cairo display driver - write bitmap (lower level functions)
 
   SPDX-FileCopyrightText: 2007-2008 Lars Ahlzen
   SPDX-FileCopyrightText: GRASS Development Team
   SPDX-License-Identifier: GPL-2.0-or-later
 
   \author Lars Ahlzen <lars ahlzen.com> (original contributor)
   \author Glynn Clements
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#include <grass/gis.h>
#include <grass/glocale.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 + ca.width * ca.height * 4);
    p = put_4(p, 0);
    p = put_4(p, HEADER_SIZE);
 
    p = put_4(p, 40);
    p = put_4(p, ca.width);
    p = put_4(p, -ca.height);
    p = put_2(p, 1);
    p = put_2(p, 32);
    p = put_4(p, 0);
    p = put_4(p, ca.width * ca.height * 4);
    p = put_4(p, 0);
    p = put_4(p, 0);
    p = put_4(p, 0);
    p = put_4(p, 0);
}
 
void cairo_write_bmp(void)
{
    unsigned char header[HEADER_SIZE];
    FILE *output;
 
    output = fopen(ca.file_name, "wb");
    if (!output)
        G_fatal_error(_("Cairo: unable to open output file <%s>"),
                      ca.file_name);
 
    memset(header, 0, sizeof(header));
    make_bmp_header(header);
    fwrite(header, sizeof(header), 1, output);
 
    fwrite(ca.grid, ca.stride, ca.height, output);
 
    fclose(output);
}