#version 450 core

//! type fragment

layout( location = 0 ) uniform sampler2D u_InputTexture;
layout( location = 1 ) uniform vec2 u_OutputSize;
layout( location = 2 ) uniform int u_SourceLOD;

layout( location = 0 ) out vec3 color;

void main( void )
{
	const vec2 c = gl_FragCoord.xy;
	color = ( .25 * (
			  textureLod( u_InputTexture , ( c + vec2( .5 , .5 ) ) / u_OutputSize , u_SourceLOD )
			+ textureLod( u_InputTexture , ( c + vec2(-.5 , .5 ) ) / u_OutputSize , u_SourceLOD )
			+ textureLod( u_InputTexture , ( c + vec2( .5 ,-.5 ) ) / u_OutputSize , u_SourceLOD )
			+ textureLod( u_InputTexture , ( c + vec2(-.5 ,-.5 ) ) / u_OutputSize , u_SourceLOD )
		) ).rgb;
}