// fpSELECT.glsl
uniform lowp		sampler2D				uTex;
uniform lowp		float						uSpriteBlurAmount;
uniform mediump vec2						uTcScale;
varying mediump vec2						vTc;
varying lowp		vec4						vColor;

mediump float normpdf(in mediump float x, in mediump float sigma)
{
				return 0.39894*exp(-0.5*x*x/(sigma*sigma))/sigma;
}

const float fSolidThreshold = 0.1;
const vec4 vHighlightColour = vec4(0.5, 0.8, 1, 1);

mediump float minDistf(in int x, in int y, in float minDist)
{
	vec2 sampleCoord = vTc + vec2(float(x), float(y))*uTcScale;
												sampleCoord = sampleCoord/uTcScale;
												sampleCoord = sampleCoord + vec2(0.5, 0.5);  // Add 0.5, since a cast to an integer always rounds down
												sampleCoord.x = float(int(sampleCoord.x));			// We're rounding to the nearest integer
												sampleCoord.y = float(int(sampleCoord.y));			// We're rounding to the nearest integer
												sampleCoord = sampleCoord + vec2(0.5, 0.5);
												sampleCoord = sampleCoord * uTcScale;		// Back into texture coordinates
												
												vec2 coordDiff = abs(vTc - sampleCoord)/uTcScale;
												
												vec4 texSample = texture2D(uTex, sampleCoord);
												if (texSample.a > fSolidThreshold)
												{
																float distance = sqrt((coordDiff.x*coordDiff.x) + (coordDiff.y*coordDiff.y));
																minDist = min(minDist, distance);
												}
												return minDist;
}

void main()
{
				// First we sample the main texel - if it's solid, we just return it.
				vec4 texColor = texture2D(uTex, vTc);
				if (texColor.a > fSolidThreshold)
				{
								gl_FragColor = mix(vHighlightColour, texColor, texColor.a);
								return;
				}
								
				int x,y;
				int kSize = 3;
				float minDist = float(kSize)+1.0;
				x = -3;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = -2;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = -1;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = 0;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = 1;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = 2;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);
				x = 3;
				y = -3;
				minDist = minDistf(x,y,minDist);
				y = -2;
				minDist = minDistf(x,y,minDist);
				y = -1;
				minDist = minDistf(x,y,minDist);
				y = 0;
				minDist = minDistf(x,y,minDist);
				y = 1;
				minDist = minDistf(x,y,minDist);
				y = 2;
				minDist = minDistf(x,y,minDist);
				y = 3;
				minDist = minDistf(x,y,minDist);

				minDist = max(0.0, minDist-1.1);
				minDist = minDist/float(kSize);
				gl_FragColor = mix(vHighlightColour, vec4(0,0,0,0), minDist);
}