#import "GPUImageFilterGroup.h"
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@class GPUImageGaussianBlurFilter;
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@class GPUImageXYDerivativeFilter;
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@class GPUImageGrayscaleFilter;
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@class GPUImageGaussianBlurFilter;
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@class GPUImageThresholdedNonMaximumSuppressionFilter;
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@class GPUImageColorPackingFilter;
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//#define DEBUGFEATUREDETECTION
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/** Harris corner detector
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First pass: reduce to luminance and take the derivative of the luminance texture (GPUImageXYDerivativeFilter)
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Second pass: blur the derivative (GPUImageGaussianBlurFilter)
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Third pass: apply the Harris corner detection calculation
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This is the Harris corner detector, as described in
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C. Harris and M. Stephens. A Combined Corner and Edge Detector. Proc. Alvey Vision Conf., Univ. Manchester, pp. 147-151, 1988.
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*/
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@interface GPUImageHarrisCornerDetectionFilter : GPUImageFilterGroup
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{
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GPUImageXYDerivativeFilter *derivativeFilter;
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GPUImageGaussianBlurFilter *blurFilter;
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GPUImageFilter *harrisCornerDetectionFilter;
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GPUImageThresholdedNonMaximumSuppressionFilter *nonMaximumSuppressionFilter;
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GPUImageColorPackingFilter *colorPackingFilter;
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GLfloat *cornersArray;
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GLubyte *rawImagePixels;
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}
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/** The radius of the underlying Gaussian blur. The default is 2.0.
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*/
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@property(readwrite, nonatomic) CGFloat blurRadiusInPixels;
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// This changes the dynamic range of the Harris corner detector by amplifying small cornerness values. Default is 5.0.
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@property(readwrite, nonatomic) CGFloat sensitivity;
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// A threshold value at which a point is recognized as being a corner after the non-maximum suppression. Default is 0.20.
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@property(readwrite, nonatomic) CGFloat threshold;
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// This block is called on the detection of new corner points, usually on every processed frame. A C array containing normalized coordinates in X, Y pairs is passed in, along with a count of the number of corners detected and the current timestamp of the video frame
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@property(nonatomic, copy) void(^cornersDetectedBlock)(GLfloat* cornerArray, NSUInteger cornersDetected, CMTime frameTime);
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// These images are only enabled when built with DEBUGFEATUREDETECTION defined, and are used to examine the intermediate states of the feature detector
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@property(nonatomic, readonly, strong) NSMutableArray *intermediateImages;
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// Initialization and teardown
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- (id)initWithCornerDetectionFragmentShader:(NSString *)cornerDetectionFragmentShader;
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@end
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