uniform sampler2D source;
uniform vec2 size;
uniform vec4 crop;
uniform float alpha;
out vec4 outColor;

void main() {
	vec2 p = vec2(gl_FragCoord.x, size.y - gl_FragCoord.y) / size;
	vec4 c = texture(source, crop.xy + p * crop.zw);
	outColor = vec4(c.rgb, c.a * alpha);
}