#import "GPUImageFASTCornerDetectionFilter.h"
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#import "GPUImageGrayscaleFilter.h"
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#import "GPUImage3x3TextureSamplingFilter.h"
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#import "GPUImageNonMaximumSuppressionFilter.h"
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// 14 total texture coordinates from vertex shader for non-dependent reads
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// 3 texture coordinates for dependent reads, then
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NSString *const kGPUImageFASTDetectorFragmentShaderString = SHADER_STRING
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(
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precision highp float;
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varying vec2 textureCoordinate;
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varying vec2 leftTextureCoordinate;
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varying vec2 rightTextureCoordinate;
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varying vec2 topTextureCoordinate;
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varying vec2 topLeftTextureCoordinate;
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varying vec2 topRightTextureCoordinate;
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varying vec2 bottomTextureCoordinate;
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varying vec2 bottomLeftTextureCoordinate;
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varying vec2 bottomRightTextureCoordinate;
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uniform sampler2D inputImageTexture;
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uniform sampler2D lookupTable;
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void main()
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{
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lowp float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;
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lowp float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
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lowp float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
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lowp float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
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lowp float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
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lowp float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
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lowp float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
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lowp float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
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lowp float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
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lowp float byteTally = 1.0 / 255.0 * step(centerIntensity, topRightIntensity);
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byteTally += 2.0 / 255.0 * step(centerIntensity, topIntensity);
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byteTally += 4.0 / 255.0 * step(centerIntensity, topLeftIntensity);
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byteTally += 8.0 / 255.0 * step(centerIntensity, leftIntensity);
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byteTally += 16.0 / 255.0 * step(centerIntensity, bottomLeftIntensity);
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byteTally += 32.0 / 255.0 * step(centerIntensity, bottomIntensity);
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byteTally += 64.0 / 255.0 * step(centerIntensity, bottomRightIntensity);
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byteTally += 128.0 / 255.0 * step(centerIntensity, rightIntensity);
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// TODO: Replace the above with a dot product and two vec4s
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// TODO: Apply step to a matrix, rather than individually
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gl_FragColor = vec4(byteTally, byteTally, byteTally, 1.0);
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}
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);
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@implementation GPUImageFASTCornerDetectionFilter
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- (id)init;
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{
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if (!(self = [self initWithFASTDetectorVariant:kGPUImageFAST12ContiguousNonMaximumSuppressed]))
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{
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return nil;
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}
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return self;
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}
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- (id)initWithFASTDetectorVariant:(GPUImageFASTDetectorType)detectorType;
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{
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if (!(self = [super init]))
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{
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return nil;
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}
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// [derivativeFilter addTarget:blurFilter];
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// [blurFilter addTarget:harrisCornerDetectionFilter];
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// [harrisCornerDetectionFilter addTarget:nonMaximumSuppressionFilter];
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// [simpleThresholdFilter addTarget:colorPackingFilter];
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// self.initialFilters = [NSArray arrayWithObjects:derivativeFilter, nil];
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// self.terminalFilter = colorPackingFilter;
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// self.terminalFilter = nonMaximumSuppressionFilter;
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return self;
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}
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@end
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