Constant MATTE_BODY

const MATTE_BODY: &str = r#"
uniform sampler2D u_b;
uniform int u_matte_alpha;
uniform int u_matte_invert;
vec4 effect(vec4 src, vec2 uv) {
    vec4 m = texture(u_b, uv);
    float k = (u_matte_alpha != 0) ? m.a : luma(m.rgb) * m.a;
    if (u_matte_invert != 0) { k = 1.0 - k; }
    return vec4(src.rgb, src.a * clamp(k, 0.0, 1.0));
}
"#;