color_rand.c

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#include <time.h>               /*  For time()  */
#include <stdio.h>              /*  For NULL */
#include <stdlib.h>             /*  For rand() and srand() */
#include <grass/gis.h>

#define MAX_COLORS 1024
#define DEVIATION 128


int G_make_random_colors(struct Colors *colors, CELL min, CELL max)
{
    unsigned char red, grn, blu;
    int count;
    CELL n;

    G_init_colors(colors);
    if (min > max)
        return -1;

    srand(time(NULL));

    count = MAX_COLORS - DEVIATION + rand() % DEVIATION;
    if (count > max - min + 1)
        count = max - min + 1;

    for (n = 1; n <= count; n++) {
        red = rand() & 0377;
        grn = rand() & 0377;
        blu = rand() & 0377;
        G_add_modular_color_rule(n, red, grn, blu, n, red, grn, blu, colors);
    }
    G_set_color_range(min, max, colors);

    return 1;
}