axmol/tests/cpp-tests/Resources/Shaders/example_GreyScale.fsh

#ifdef GL_ES
precision mediump float;
#endif

varying vec4 v_fragmentColor;
varying vec2 v_texCoord;

uniform sampler2D u_texture;

void main(void)
{
	vec4 c = texture2D(u_texture, v_texCoord);
	gl_FragColor.xyz = vec3(0.2126*c.r + 0.7152*c.g + 0.0722*c.b);
	gl_FragColor.w = c.w;
}