rgba_to_rgb.c

unsigned char *
rgba_to_rgb(unsigned char *rgba, int rgba_size)
{
    int rgb_size = rgba_size/4*3;
    unsigned char *rgb = malloc(sizeof(unsigned char)*rgb_size);
    if (!rgb) return NULL;
    int i, j;
    for (i=0,j=0;i<rgba_size;i+=4,j+=3) {
        rgb[j] = *(rgba+i);
        rgb[j+1] = *(rgba+i+1);
        rgb[j+2] = *(rgba+i+2);
    }
    return rgb;
}