#version 300 es

precision highp float;

in vec2 v_texcoord;
uniform sampler2D tex;
out vec4 fragColor;

void main() {
	vec4 pixColor = texture(tex, v_texcoord);
	float gray = 0.0;

	// Get gray with luminosity and hdr
	// https://en.wikipedia.org/wiki/Grayscale#Luma_coding_in_video_systems
	gray = dot(pixColor.rgb, vec3(0.2627, 0.6780, 0.0593));

	// Change contrast
	float contrast = 0.95; 
	gray = (gray - 0.5) * contrast + 0.5;
	gray = clamp(gray, 0.0, 1.0);

	fragColor = vec4(vec3(gray), pixColor.a);
}