bilateralFilter.metal

#include <metal_stdlib>
using namespace metal;
#include <CoreImage/CoreImage.h>

extern "C" { namespace coreimage {
	float4 bilateralFilter(sampler src, float2 texelOffset, float distanceNormalizationFactor, destination dest) {
		const int gaussianSamples = 9;

		float2 blurCoordinates[9];
		for (int i = 0; i < gaussianSamples; i++) {
			int multiplier = i - (gaussianSamples - 1) / 2;
			float2 blurStep = float(multiplier) * texelOffset;
			blurCoordinates[i] = dest.coord() + blurStep;
		}

		float4 centralColor = src.sample(src.transform(blurCoordinates[4]));
		float gaussianWeightTotal = 0.18;
		float4 sum = centralColor * gaussianWeightTotal;

		float4 sampleColor;
		float distanceFromCentralColor;
		float gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[0]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.05 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[1]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.09 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[2]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.12 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[3]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.15 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[5]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.15 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[6]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.12 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[7]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.09 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		sampleColor = src.sample(src.transform(blurCoordinates[8]));
		distanceFromCentralColor = min(distance(centralColor, sampleColor) * distanceNormalizationFactor, 1.0);
		gaussianWeight = 0.05 * (1.0 - distanceFromCentralColor);
		gaussianWeightTotal += gaussianWeight;
		sum += sampleColor * gaussianWeight;

		return sum / gaussianWeightTotal;
	}
}}