mkxp-z/shader/gray.frag

uniform sampler2D texture;
uniform lowp float gray;

varying vec2 v_texCoord;

const vec3 lumaF = vec3(.299, .587, .114);

void main()
{
	/* Sample source color */
	vec4 frag = texture2D(texture, v_texCoord);

	/* Apply gray */
	float luma = dot(frag.rgb, lumaF);
	frag.rgb = mix(frag.rgb, vec3(luma), gray);

	gl_FragColor = frag;
}