ProjectArcade

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// Spline36 upscaling shader.
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// See issue #3921
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// Modified as per #15566
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#ifdef GL_ES
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precision mediump float;
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precision mediump int;
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#endif
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uniform sampler2D sampler0;
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varying vec2 v_position;
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uniform vec2 u_texelDelta;
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uniform vec2 u_pixelDelta;
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const vec2 HALF_PIXEL = vec2(0.5, 0.5);
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float spline36_0_1(float x) {
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	return ((13.0 / 11.0 * x - 453.0 / 209.0) * x - 3.0 / 209.0) * x + 1.0;
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}
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float spline36_1_2(float x) {
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	return ((-6.0 / 11.0 * x + 612.0 / 209.0) * x - 1038.0 / 209.0) * x + 540.0 / 209.0;
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}
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float spline36_2_3(float x) {
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	return ((1.0 / 11.0 * x - 159.0 / 209.0) * x + 434.0 / 209.0) * x - 384.0 / 209.0;
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}
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vec4 rgb(int inputX, int inputY) {
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	return texture2D(sampler0, (vec2(inputX, inputY) + HALF_PIXEL) * u_texelDelta);
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}
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vec4 interpolateHorizontally(vec2 inputPos, ivec2 inputPosFloor, int dy) {
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	float sumOfWeights = 0.0;
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	vec4 sumOfWeightedPixel = vec4(0.0);
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	float x;
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	float weight;
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	x = inputPos.x - float(inputPosFloor.x - 2);
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	weight = spline36_2_3(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x - 2, inputPosFloor.y + dy);
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	--x;
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	weight = spline36_1_2(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x - 1, inputPosFloor.y + dy);
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	--x;
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	weight = spline36_0_1(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x + 0, inputPosFloor.y + dy);
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	x = 1.0 - x;
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	weight = spline36_0_1(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x + 1, inputPosFloor.y + dy);
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	++x;
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	weight = spline36_1_2(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x + 2, inputPosFloor.y + dy);
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	++x;
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	weight = spline36_2_3(x);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * rgb(inputPosFloor.x + 3, inputPosFloor.y + dy);
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	return sumOfWeightedPixel / sumOfWeights;
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}
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vec4 process(vec2 outputPos) {
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	vec2 inputPos = outputPos / u_texelDelta - HALF_PIXEL;
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	ivec2 inputPosFloor = ivec2(inputPos);
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	// Vertical interporation
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	float sumOfWeights = 0.0;
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	vec4 sumOfWeightedPixel = vec4(0.0);
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	float weight;
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	float y;
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	y = inputPos.y - float(inputPosFloor.y - 2);
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	weight = spline36_2_3(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, -2);
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	--y;
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	weight = spline36_1_2(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, -1);
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	--y;
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	weight = spline36_0_1(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, +0);
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	y = 1.0 - y;
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	weight = spline36_0_1(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, +1);
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	++y;
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	weight = spline36_1_2(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, +2);
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	++y;
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	weight = spline36_2_3(y);
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	sumOfWeights += weight;
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	sumOfWeightedPixel += weight * interpolateHorizontally(inputPos, inputPosFloor, +3);
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	return vec4((sumOfWeightedPixel / sumOfWeights).xyz, 1.0);
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}
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void main()
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{
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  gl_FragColor.rgba = process(v_position);
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}
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