#import "GPUImageDirectionalSobelEdgeDetectionFilter.h"
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@implementation GPUImageDirectionalSobelEdgeDetectionFilter
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageDirectionalSobelEdgeDetectionFragmentShaderString = SHADER_STRING
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(
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precision mediump 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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void main()
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{
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float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
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float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
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float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
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float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
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float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
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float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
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float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
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float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
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vec2 gradientDirection;
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gradientDirection.x = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
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gradientDirection.y = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
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float gradientMagnitude = length(gradientDirection);
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vec2 normalizedDirection = normalize(gradientDirection);
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normalizedDirection = sign(normalizedDirection) * floor(abs(normalizedDirection) + 0.617316); // Offset by 1-sin(pi/8) to set to 0 if near axis, 1 if away
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normalizedDirection = (normalizedDirection + 1.0) * 0.5; // Place -1.0 - 1.0 within 0 - 1.0
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gl_FragColor = vec4(gradientMagnitude, normalizedDirection.x, normalizedDirection.y, 1.0);
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}
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);
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#else
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NSString *const kGPUImageDirectionalSobelEdgeDetectionFragmentShaderString = SHADER_STRING
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(
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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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void main()
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{
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float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
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float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
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float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
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float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
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float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
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float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
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float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
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float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
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vec2 gradientDirection;
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gradientDirection.x = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
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gradientDirection.y = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
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float gradientMagnitude = length(gradientDirection);
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vec2 normalizedDirection = normalize(gradientDirection);
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normalizedDirection = sign(normalizedDirection) * floor(abs(normalizedDirection) + 0.617316); // Offset by 1-sin(pi/8) to set to 0 if near axis, 1 if away
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normalizedDirection = (normalizedDirection + 1.0) * 0.5; // Place -1.0 - 1.0 within 0 - 1.0
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gl_FragColor = vec4(gradientMagnitude, normalizedDirection.x, normalizedDirection.y, 1.0);
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}
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);
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#endif
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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:kGPUImageDirectionalSobelEdgeDetectionFragmentShaderString]))
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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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@end
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