camembert

#include <Imlib2.h>
#include <math.h>
#include <stdio.h>

static int u, v;

int compute(int w, int h)
{
    u = cosf(60.f * 3.14159f / 180.f) * h;
    v = sinf(60.f * 3.14159f / 180.f) * h;
}

int collide(int x, int y, int w, int h)
{
    int t = x - w/2;

    return
        h - y < sqrtf(h*h - t*t)    && // circle bound
        h - y >  v * t / u          && // bottom-right bound
        h - y > -v * t / u           ; // bottom-left bound
}

int main(int argc, char **argv)
{
    Imlib_Image img;
    Imlib_Image cropped_img;
    DATA32 *data;
    int w, h;
    int i, j;

    if (argc != 3)
        return 1;

    img = imlib_load_image(argv[1]);

    if (!img)
        return 2;

    imlib_context_set_image(img);
    imlib_image_set_has_alpha(1);

    data = imlib_image_get_data();
    w = imlib_image_get_width();
    h = imlib_image_get_height();

    compute(w, h);

    for (i=0; i<h; i++)
    {
        for (j=0; j<w; j++)
        {
            if (!collide(j, i, w, h))
                *data = 0; // Fully transparent black

            data++;
        }
    }

    cropped_img = imlib_create_cropped_image(w/2 - u, 0, 2*u, h);
    imlib_free_image_and_decache();

    imlib_context_set_image(cropped_img);
    imlib_save_image(argv[2]);
    imlib_free_image_and_decache();

    return 0;
}