a2aa5934996a9ae9ef0de5276b37ed4bfd6e3ca1.svn-base
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#import "GPUImageShiTomasiFeatureDetectionFilter.h"
@implementation GPUImageShiTomasiFeatureDetectionFilter
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageShiTomasiCornerDetectionFragmentShaderString = SHADER_STRING
(
varying highp vec2 textureCoordinate;
uniform sampler2D inputImageTexture;
uniform lowp float sensitivity;
void main()
{
mediump vec3 derivativeElements = texture2D(inputImageTexture, textureCoordinate).rgb;
mediump float derivativeDifference = derivativeElements.x - derivativeElements.y;
mediump float zElement = (derivativeElements.z * 2.0) - 1.0;
// R = Ix^2 + Iy^2 - sqrt( (Ix^2 - Iy^2)^2 + 4 * Ixy * Ixy)
mediump float cornerness = derivativeElements.x + derivativeElements.y - sqrt(derivativeDifference * derivativeDifference + 4.0 * zElement * zElement);
gl_FragColor = vec4(vec3(cornerness * sensitivity), 1.0);
}
);
#else
NSString *const kGPUImageShiTomasiCornerDetectionFragmentShaderString = SHADER_STRING
(
varying vec2 textureCoordinate;
uniform sampler2D inputImageTexture;
uniform float sensitivity;
void main()
{
vec3 derivativeElements = texture2D(inputImageTexture, textureCoordinate).rgb;
float derivativeDifference = derivativeElements.x - derivativeElements.y;
float zElement = (derivativeElements.z * 2.0) - 1.0;
// R = Ix^2 + Iy^2 - sqrt( (Ix^2 - Iy^2)^2 + 4 * Ixy * Ixy)
float cornerness = derivativeElements.x + derivativeElements.y - sqrt(derivativeDifference * derivativeDifference + 4.0 * zElement * zElement);
gl_FragColor = vec4(vec3(cornerness * sensitivity), 1.0);
}
);
#endif
#pragma mark -
#pragma mark Initialization and teardown
- (id)init;
{
if (!(self = [self initWithCornerDetectionFragmentShader:kGPUImageShiTomasiCornerDetectionFragmentShaderString]))
{
return nil;
}
self.sensitivity = 1.5;
return self;
}
@end