#import "GPUImageDirectionalNonMaximumSuppressionFilter.h"
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@implementation GPUImageDirectionalNonMaximumSuppressionFilter
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageDirectionalNonmaximumSuppressionFragmentShaderString = SHADER_STRING
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(
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precision mediump float;
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varying highp vec2 textureCoordinate;
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uniform sampler2D inputImageTexture;
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uniform highp float texelWidth;
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uniform highp float texelHeight;
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uniform mediump float upperThreshold;
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uniform mediump float lowerThreshold;
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void main()
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{
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vec3 currentGradientAndDirection = texture2D(inputImageTexture, textureCoordinate).rgb;
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vec2 gradientDirection = ((currentGradientAndDirection.gb * 2.0) - 1.0) * vec2(texelWidth, texelHeight);
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float firstSampledGradientMagnitude = texture2D(inputImageTexture, textureCoordinate + gradientDirection).r;
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float secondSampledGradientMagnitude = texture2D(inputImageTexture, textureCoordinate - gradientDirection).r;
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float multiplier = step(firstSampledGradientMagnitude, currentGradientAndDirection.r);
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multiplier = multiplier * step(secondSampledGradientMagnitude, currentGradientAndDirection.r);
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float thresholdCompliance = smoothstep(lowerThreshold, upperThreshold, currentGradientAndDirection.r);
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multiplier = multiplier * thresholdCompliance;
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gl_FragColor = vec4(multiplier, multiplier, multiplier, 1.0);
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}
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);
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#else
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NSString *const kGPUImageDirectionalNonmaximumSuppressionFragmentShaderString = SHADER_STRING
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(
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varying vec2 textureCoordinate;
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uniform sampler2D inputImageTexture;
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uniform float texelWidth;
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uniform float texelHeight;
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uniform float upperThreshold;
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uniform float lowerThreshold;
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void main()
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{
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vec3 currentGradientAndDirection = texture2D(inputImageTexture, textureCoordinate).rgb;
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vec2 gradientDirection = ((currentGradientAndDirection.gb * 2.0) - 1.0) * vec2(texelWidth, texelHeight);
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float firstSampledGradientMagnitude = texture2D(inputImageTexture, textureCoordinate + gradientDirection).r;
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float secondSampledGradientMagnitude = texture2D(inputImageTexture, textureCoordinate - gradientDirection).r;
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float multiplier = step(firstSampledGradientMagnitude, currentGradientAndDirection.r);
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multiplier = multiplier * step(secondSampledGradientMagnitude, currentGradientAndDirection.r);
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float thresholdCompliance = smoothstep(lowerThreshold, upperThreshold, currentGradientAndDirection.r);
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multiplier = multiplier * thresholdCompliance;
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gl_FragColor = vec4(multiplier, multiplier, multiplier, 1.0);
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}
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);
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#endif
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@synthesize texelWidth = _texelWidth;
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@synthesize texelHeight = _texelHeight;
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@synthesize upperThreshold = _upperThreshold;
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@synthesize lowerThreshold = _lowerThreshold;
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#pragma mark -
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#pragma mark Initialization and teardown
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- (id)init;
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{
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if (!(self = [super initWithFragmentShaderFromString:kGPUImageDirectionalNonmaximumSuppressionFragmentShaderString]))
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{
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return nil;
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}
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texelWidthUniform = [filterProgram uniformIndex:@"texelWidth"];
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texelHeightUniform = [filterProgram uniformIndex:@"texelHeight"];
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upperThresholdUniform = [filterProgram uniformIndex:@"upperThreshold"];
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lowerThresholdUniform = [filterProgram uniformIndex:@"lowerThreshold"];
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self.upperThreshold = 0.5;
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self.lowerThreshold = 0.1;
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return self;
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}
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- (void)setupFilterForSize:(CGSize)filterFrameSize;
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{
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if (!hasOverriddenImageSizeFactor)
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{
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_texelWidth = 1.0 / filterFrameSize.width;
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_texelHeight = 1.0 / filterFrameSize.height;
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runSynchronouslyOnVideoProcessingQueue(^{
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[GPUImageContext setActiveShaderProgram:filterProgram];
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glUniform1f(texelWidthUniform, _texelWidth);
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glUniform1f(texelHeightUniform, _texelHeight);
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});
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}
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}
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#pragma mark -
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#pragma mark Accessors
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- (void)setTexelWidth:(CGFloat)newValue;
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{
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hasOverriddenImageSizeFactor = YES;
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_texelWidth = newValue;
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[self setFloat:_texelWidth forUniform:texelWidthUniform program:filterProgram];
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}
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- (void)setTexelHeight:(CGFloat)newValue;
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{
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hasOverriddenImageSizeFactor = YES;
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_texelHeight = newValue;
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[self setFloat:_texelHeight forUniform:texelHeightUniform program:filterProgram];
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}
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- (void)setLowerThreshold:(CGFloat)newValue;
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{
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_lowerThreshold = newValue;
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[self setFloat:_lowerThreshold forUniform:lowerThresholdUniform program:filterProgram];
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}
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- (void)setUpperThreshold:(CGFloat)newValue;
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{
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_upperThreshold = newValue;
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[self setFloat:_upperThreshold forUniform:upperThresholdUniform program:filterProgram];
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}
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@end
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