#include <cairo.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
    double angle = 0.5, radmul=1;

    if (argc >= 2)
	angle = atof(argv[1]);

    cairo_surface_t *img = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 200, 200);
    cairo_pattern_t *rg = cairo_pattern_create_radial(0, 0, 1,
						      radmul*cos(angle),
						      radmul*sin(angle),
						      0);
    cairo_pattern_add_color_stop_rgb(rg, 0.0, 0, 1, 0);
    cairo_pattern_add_color_stop_rgb(rg, 1.0, 1, 0, 0);
    cairo_t *ct = cairo_create(img);
    cairo_translate(ct, 100, 100);
    cairo_scale(ct, 10, -10);
    cairo_set_source(ct, rg);
    cairo_paint(ct);
    cairo_surface_write_to_png(img, "radial-focus.png");

    return 0;
}