#version 330

#define FLAG_RED    (1<<0)
#define FLAG_GREEN  (1<<1)
#define FLAG_BLUE   (1<<2)
#define FLAG_ALPHA  (1<<3)
#define FLAG_COLORS (FLAG_RED | FLAG_GREEN | FLAG_BLUE | FLAG_ALPHA)

#define FLAG_LINEAR (1<<4)

uniform sampler2D tex;
uniform int flags;

in vec2 fragUV;
in vec4 fragColor;

out vec4 outputColor;

const float gamma = 2.2;

void main() {
	if ((flags & FLAG_COLORS) == FLAG_RED) {
		outputColor = vec4(fragColor.rgb, fragColor.a * texture(tex, fragUV.st).r);
	} else {
		vec4 color = texture(tex, fragUV.st);
		if ((flags & FLAG_LINEAR) != 0)
			color.rgb = pow(color.rgb, vec3(1.0/gamma));
		outputColor = color * fragColor;
		if ((flags & FLAG_ALPHA) == 0)
			outputColor.a = 1;
	}
}