#import "GPUImageThresholdEdgeDetectionFilter.h"
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@implementation GPUImageThresholdEdgeDetectionFilter
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// Invert the colorspace for a sketch
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
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NSString *const kGPUImageThresholdEdgeDetectionFragmentShaderString = 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 lowp float threshold;
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uniform float edgeStrength;
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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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float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;
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// float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
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// float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
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// float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + leftIntensity + 2.0 * centerIntensity + rightIntensity;
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// float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomIntensity + 2.0 * centerIntensity + topIntensity;
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float h = (centerIntensity - topIntensity) + (bottomIntensity - centerIntensity);
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float v = (centerIntensity - leftIntensity) + (rightIntensity - centerIntensity);
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// float h = (centerIntensity - topIntensity);
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// float j = (topIntensity - centerIntensity);
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// h = max(h,j);
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// j = abs(h);
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// float v = (centerIntensity - leftIntensity);
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float mag = length(vec2(h, v)) * edgeStrength;
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mag = step(threshold, mag);
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// float mag = abs(h);
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// gl_FragColor = vec4(h, h, h, 1.0);
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// gl_FragColor = vec4(texture2D(inputImageTexture, textureCoordinate));
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// gl_FragColor = vec4(h, centerIntensity, j, 1.0);
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gl_FragColor = vec4(mag, mag, mag, 1.0);
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}
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);
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#else
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NSString *const kGPUImageThresholdEdgeDetectionFragmentShaderString = 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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uniform float threshold;
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uniform float edgeStrength;
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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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float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
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h = max(0.0, h);
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float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
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v = max(0.0, v);
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float mag = length(vec2(h, v)) * edgeStrength;
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mag = step(threshold, mag);
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gl_FragColor = vec4(vec3(mag), 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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@synthesize threshold = _threshold;
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- (id)initWithFragmentShaderFromString:(NSString *)fragmentShaderString;
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{
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if (!(self = [super initWithFragmentShaderFromString:fragmentShaderString]))
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{
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return nil;
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}
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thresholdUniform = [secondFilterProgram uniformIndex:@"threshold"];
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self.threshold = 0.25;
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self.edgeStrength = 1.0;
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return self;
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}
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- (id)init;
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{
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if (!(self = [self initWithFragmentShaderFromString:kGPUImageThresholdEdgeDetectionFragmentShaderString]))
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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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#pragma mark -
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#pragma mark Accessors
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- (void)setThreshold:(CGFloat)newValue;
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{
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_threshold = newValue;
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[self setFloat:_threshold forUniform:thresholdUniform program:secondFilterProgram];
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}
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@end
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