/*
 * Set the current image (Imlib2::Image).
 *
 * Note that this function is not useful at the moment since all image
 * instance methods blindly blow away the image and color context.  So
 * you cannot safely mix image context and image instance methods.
 *
 * Example:
 *   ctx.image = image
 *
 */
static VALUE ctx_set_image(VALUE self, VALUE val) {