#import "GPUImageSingleComponentGaussianBlurFilter.h"
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@implementation GPUImageSingleComponentGaussianBlurFilter
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+ (NSString *)vertexShaderForOptimizedBlurOfRadius:(NSUInteger)blurRadius sigma:(CGFloat)sigma;
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{
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if (blurRadius < 1)
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{
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return kGPUImageVertexShaderString;
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}
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// First, generate the normal Gaussian weights for a given sigma
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GLfloat *standardGaussianWeights = calloc(blurRadius + 1, sizeof(GLfloat));
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GLfloat sumOfWeights = 0.0;
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for (NSUInteger currentGaussianWeightIndex = 0; currentGaussianWeightIndex < blurRadius + 1; currentGaussianWeightIndex++)
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{
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standardGaussianWeights[currentGaussianWeightIndex] = (1.0 / sqrt(2.0 * M_PI * pow(sigma, 2.0))) * exp(-pow(currentGaussianWeightIndex, 2.0) / (2.0 * pow(sigma, 2.0)));
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if (currentGaussianWeightIndex == 0)
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{
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sumOfWeights += standardGaussianWeights[currentGaussianWeightIndex];
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}
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else
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{
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sumOfWeights += 2.0 * standardGaussianWeights[currentGaussianWeightIndex];
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}
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}
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// Next, normalize these weights to prevent the clipping of the Gaussian curve at the end of the discrete samples from reducing luminance
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for (NSUInteger currentGaussianWeightIndex = 0; currentGaussianWeightIndex < blurRadius + 1; currentGaussianWeightIndex++)
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{
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standardGaussianWeights[currentGaussianWeightIndex] = standardGaussianWeights[currentGaussianWeightIndex] / sumOfWeights;
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}
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// From these weights we calculate the offsets to read interpolated values from
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NSUInteger numberOfOptimizedOffsets = MIN(blurRadius / 2 + (blurRadius % 2), 7);
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GLfloat *optimizedGaussianOffsets = calloc(numberOfOptimizedOffsets, sizeof(GLfloat));
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for (NSUInteger currentOptimizedOffset = 0; currentOptimizedOffset < numberOfOptimizedOffsets; currentOptimizedOffset++)
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{
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GLfloat firstWeight = standardGaussianWeights[currentOptimizedOffset*2 + 1];
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GLfloat secondWeight = standardGaussianWeights[currentOptimizedOffset*2 + 2];
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GLfloat optimizedWeight = firstWeight + secondWeight;
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optimizedGaussianOffsets[currentOptimizedOffset] = (firstWeight * (currentOptimizedOffset*2 + 1) + secondWeight * (currentOptimizedOffset*2 + 2)) / optimizedWeight;
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}
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NSMutableString *shaderString = [[NSMutableString alloc] init];
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// Header
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[shaderString appendFormat:@"\
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attribute vec4 position;\n\
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attribute vec4 inputTextureCoordinate;\n\
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\n\
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uniform float texelWidthOffset;\n\
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uniform float texelHeightOffset;\n\
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\n\
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varying vec2 blurCoordinates[%lu];\n\
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\n\
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void main()\n\
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{\n\
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gl_Position = position;\n\
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\n\
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vec2 singleStepOffset = vec2(texelWidthOffset, texelHeightOffset);\n", (unsigned long)(1 + (numberOfOptimizedOffsets * 2))];
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// Inner offset loop
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[shaderString appendString:@"blurCoordinates[0] = inputTextureCoordinate.xy;\n"];
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for (NSUInteger currentOptimizedOffset = 0; currentOptimizedOffset < numberOfOptimizedOffsets; currentOptimizedOffset++)
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{
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[shaderString appendFormat:@"\
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blurCoordinates[%lu] = inputTextureCoordinate.xy + singleStepOffset * %f;\n\
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blurCoordinates[%lu] = inputTextureCoordinate.xy - singleStepOffset * %f;\n", (unsigned long)((currentOptimizedOffset * 2) + 1), optimizedGaussianOffsets[currentOptimizedOffset], (unsigned long)((currentOptimizedOffset * 2) + 2), optimizedGaussianOffsets[currentOptimizedOffset]];
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}
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// Footer
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[shaderString appendString:@"}\n"];
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free(optimizedGaussianOffsets);
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free(standardGaussianWeights);
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return shaderString;
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}
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+ (NSString *)fragmentShaderForOptimizedBlurOfRadius:(NSUInteger)blurRadius sigma:(CGFloat)sigma;
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{
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if (blurRadius < 1)
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{
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return kGPUImagePassthroughFragmentShaderString;
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}
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// First, generate the normal Gaussian weights for a given sigma
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GLfloat *standardGaussianWeights = calloc(blurRadius + 1, sizeof(GLfloat));
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GLfloat sumOfWeights = 0.0;
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for (NSUInteger currentGaussianWeightIndex = 0; currentGaussianWeightIndex < blurRadius + 1; currentGaussianWeightIndex++)
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{
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standardGaussianWeights[currentGaussianWeightIndex] = (1.0 / sqrt(2.0 * M_PI * pow(sigma, 2.0))) * exp(-pow(currentGaussianWeightIndex, 2.0) / (2.0 * pow(sigma, 2.0)));
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if (currentGaussianWeightIndex == 0)
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{
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sumOfWeights += standardGaussianWeights[currentGaussianWeightIndex];
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}
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else
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{
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sumOfWeights += 2.0 * standardGaussianWeights[currentGaussianWeightIndex];
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}
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}
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// Next, normalize these weights to prevent the clipping of the Gaussian curve at the end of the discrete samples from reducing luminance
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for (NSUInteger currentGaussianWeightIndex = 0; currentGaussianWeightIndex < blurRadius + 1; currentGaussianWeightIndex++)
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{
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standardGaussianWeights[currentGaussianWeightIndex] = standardGaussianWeights[currentGaussianWeightIndex] / sumOfWeights;
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}
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// From these weights we calculate the offsets to read interpolated values from
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NSUInteger numberOfOptimizedOffsets = MIN(blurRadius / 2 + (blurRadius % 2), 7);
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NSUInteger trueNumberOfOptimizedOffsets = blurRadius / 2 + (blurRadius % 2);
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NSMutableString *shaderString = [[NSMutableString alloc] init];
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// Header
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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[shaderString appendFormat:@"\
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uniform sampler2D inputImageTexture;\n\
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uniform highp float texelWidthOffset;\n\
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uniform highp float texelHeightOffset;\n\
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\n\
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varying highp vec2 blurCoordinates[%lu];\n\
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\n\
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void main()\n\
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{\n\
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lowp float sum = 0.0;\n", (unsigned long)(1 + (numberOfOptimizedOffsets * 2)) ];
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#else
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[shaderString appendFormat:@"\
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uniform sampler2D inputImageTexture;\n\
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uniform float texelWidthOffset;\n\
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uniform float texelHeightOffset;\n\
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\n\
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varying vec2 blurCoordinates[%lu];\n\
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\n\
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void main()\n\
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{\n\
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float sum = 0.0;\n", 1 + (numberOfOptimizedOffsets * 2) ];
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#endif
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// Inner texture loop
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[shaderString appendFormat:@"sum += texture2D(inputImageTexture, blurCoordinates[0]).r * %f;\n", standardGaussianWeights[0]];
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for (NSUInteger currentBlurCoordinateIndex = 0; currentBlurCoordinateIndex < numberOfOptimizedOffsets; currentBlurCoordinateIndex++)
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{
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GLfloat firstWeight = standardGaussianWeights[currentBlurCoordinateIndex * 2 + 1];
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GLfloat secondWeight = standardGaussianWeights[currentBlurCoordinateIndex * 2 + 2];
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GLfloat optimizedWeight = firstWeight + secondWeight;
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[shaderString appendFormat:@"sum += texture2D(inputImageTexture, blurCoordinates[%lu]).r * %f;\n", (unsigned long)((currentBlurCoordinateIndex * 2) + 1), optimizedWeight];
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[shaderString appendFormat:@"sum += texture2D(inputImageTexture, blurCoordinates[%lu]).r * %f;\n", (unsigned long)((currentBlurCoordinateIndex * 2) + 2), optimizedWeight];
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}
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// If the number of required samples exceeds the amount we can pass in via varyings, we have to do dependent texture reads in the fragment shader
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if (trueNumberOfOptimizedOffsets > numberOfOptimizedOffsets)
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{
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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[shaderString appendString:@"highp vec2 singleStepOffset = vec2(texelWidthOffset, texelHeightOffset);\n"];
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#else
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[shaderString appendString:@"highp vec2 singleStepOffset = vec2(texelWidthOffset, texelHeightOffset);\n"];
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#endif
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for (NSUInteger currentOverlowTextureRead = numberOfOptimizedOffsets; currentOverlowTextureRead < trueNumberOfOptimizedOffsets; currentOverlowTextureRead++)
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{
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GLfloat firstWeight = standardGaussianWeights[currentOverlowTextureRead * 2 + 1];
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GLfloat secondWeight = standardGaussianWeights[currentOverlowTextureRead * 2 + 2];
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GLfloat optimizedWeight = firstWeight + secondWeight;
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GLfloat optimizedOffset = (firstWeight * (currentOverlowTextureRead * 2 + 1) + secondWeight * (currentOverlowTextureRead * 2 + 2)) / optimizedWeight;
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[shaderString appendFormat:@"sum += texture2D(inputImageTexture, blurCoordinates[0] + singleStepOffset * %f).r * %f;\n", optimizedOffset, optimizedWeight];
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[shaderString appendFormat:@"sum += texture2D(inputImageTexture, blurCoordinates[0] - singleStepOffset * %f).r * %f;\n", optimizedOffset, optimizedWeight];
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}
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}
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// Footer
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[shaderString appendString:@"\
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gl_FragColor = vec4(sum, sum, sum, 1.0);\n\
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}\n"];
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free(standardGaussianWeights);
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return shaderString;
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}
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@end
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