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  • iOS实现图像素描效果

      使用GPUImageSketchFilter对象实现图像素描效果

    NSString *const kGPUImageSketchFragmentShaderString = SHADER_STRING
    (
     precision mediump float;
     
     varying vec2 textureCoordinate;
     varying vec2 leftTextureCoordinate;
     varying vec2 rightTextureCoordinate;
     
     varying vec2 topTextureCoordinate;
     varying vec2 topLeftTextureCoordinate;
     varying vec2 topRightTextureCoordinate;
     
     varying vec2 bottomTextureCoordinate;
     varying vec2 bottomLeftTextureCoordinate;
     varying vec2 bottomRightTextureCoordinate;
     
     uniform float edgeStrength;
    
     uniform sampler2D inputImageTexture;
     
     void main()
     {
         float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
         float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
         float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
         float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
         float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
         float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
         float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
         float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
         float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
         float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
         
         float mag = 1.0 - (length(vec2(h, v)) * edgeStrength);
         
         gl_FragColor = vec4(vec3(mag), 1.0);
     }
    );
    + (UIImage *)applySketchFilter:(UIImage *)image
    {
        GPUImageSketchFilter *filter = [[GPUImageSketchFilter alloc] init];
        
        [filter forceProcessingAtSize:image.size];
        GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image];
        [pic addTarget:filter];
        [pic processImage];
        [filter useNextFrameForImageCapture];
        
        return [filter imageFromCurrentFramebuffer];
    }

      

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  • 原文地址:https://www.cnblogs.com/salam/p/5150106.html
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