Greyscale in glsl

GLSL_contrast

float contrast(float mValue, float mScale, float mMidPoint) {
	return clamp( (mValue - mMidPoint) * mScale + mMidPoint, 0.0, 1.0);
}

float contrast(float mValue, float mScale) {
	return contrast(mValue,  mScale, .5);
}

vec3 contrast(vec3 mValue, float mScale, float mMidPoint) {
	return vec3( contrast(mValue.r, mScale, mMidPoint), contrast(mValue.g, mScale, mMidPoint), contrast(mValue.b, mScale, mMidPoint) );
}

vec3 contrast(vec3 mValue, float mScale) {
	return contrast(mValue, mScale, .5);
}

GLSL_greyscale

void main(void) {
	vec4 color = texture2D(uSampler0, vTextureCoord);
	float gray = dot(color.rgb, vec3(0.299, 0.587, 0.114));
	gl_FragColor = vec4(vec3(gray), 1.0);
}