#version 300 es
precision mediump float;

in vec2 vertTexCoord;

uniform sampler2D colorTexture;

out vec4 fragColor;

void addSample(inout vec4 color, ivec2 offset, inout float sampleCount) {
	vec4 sample = texelFetch(colorTexture, ivec2(vertTexCoord) + offset, 0);
	if (sample.a > 0.0) {
		color += sample;
		sampleCount += 1.0;
	}
}

void main() {
	fragColor = texelFetch(colorTexture, ivec2(vertTexCoord), 0);
	if (fragColor.a == 0.0) {
		float sampleCount = 0.0;
		addSample(fragColor, ivec2(-1, 0), sampleCount);
		addSample(fragColor, ivec2(1, 0), sampleCount);
		addSample(fragColor, ivec2(0, -1), sampleCount);
		addSample(fragColor, ivec2(0, 1), sampleCount);
		if (sampleCount == 0.0) {
			addSample(fragColor, ivec2(-1, -1), sampleCount);
			addSample(fragColor, ivec2(1, -1), sampleCount);
			addSample(fragColor, ivec2(-1, 1), sampleCount);
			addSample(fragColor, ivec2(1, 1), sampleCount);
		}
		if (sampleCount > 0.0) {
			fragColor /= sampleCount;
		}
	}
}