Pixel-Composer/shaders/sh_alpha_grey/sh_alpha_grey.fsh

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

uniform float brightness;
uniform float contrast;

void main() {
    vec4 col = v_vColour * texture2D( gm_BaseTexture, v_vTexcoord );
	gl_FragColor = vec4(vec3(col.a), 1.);
}