Pixel-Composer/shaders/sh_threshold/sh_threshold.fsh

//
// Simple passthrough fragment shader
//
varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform int       bright;
uniform vec2      brightThreshold;
uniform int       brightThresholdUseSurf;
uniform sampler2D brightThresholdSurf;
uniform float     brightSmooth;

uniform int       alpha;
uniform vec2      alphaThreshold;
uniform int       alphaThresholdUseSurf;
uniform sampler2D alphaThresholdSurf;
uniform float     alphaSmooth;

float _step( in float threshold, in float val ) { return val < threshold? 0. : 1.; }

void main() {
	float bri = brightThreshold.x;
	if(brightThresholdUseSurf == 1) {
		vec4 _vMap = texture2D( brightThresholdSurf, v_vTexcoord );
		bri = mix(brightThreshold.x, brightThreshold.y, (_vMap.r + _vMap.g + _vMap.b) / 3.);
	}
	
	float alp = alphaThreshold.x;
	if(alphaThresholdUseSurf == 1) {
		vec4 _vMap = texture2D( alphaThresholdSurf, v_vTexcoord );
		alp = mix(alphaThreshold.x, alphaThreshold.y, (_vMap.r + _vMap.g + _vMap.b) / 3.);
	}
	
	vec4 col  = v_vColour * texture2D( gm_BaseTexture, v_vTexcoord );
	
	if(bright == 1) {
		float bright = dot(col.rgb, vec3(0.2126, 0.7152, 0.0722));
		col.rgb = vec3(brightSmooth == 0.? _step(bri, bright) : smoothstep(bri - brightSmooth, bri + brightSmooth, bright));
	}
	
	if(alpha == 1) {
		col.a = alphaSmooth == 0.? _step(alp, col.a) : smoothstep(alp - alphaSmooth, alp + alphaSmooth, col.a);
	}
	
    gl_FragColor = col;
}