IOS OpenGL ES GPUImage 图像 XYDerivative 边缘检测 GPUImageXYDerivativeFilter

一.简介
二.效果演示
三.源码下载
四.猜你喜欢

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一.简介

GPUImage 共 125 个滤镜, 分为四类

1、Color adjustments : 31 filters , 颜色处理相关
2、Image processing : 40 filters , 图像处理相关.
3、Blending modes : 29 filters , 混合模式相关.
4、Visual effects : 25 filters , 视觉效果相关.

GPUImageXYDerivativeFilter 属于 GPUImage 图像视觉效果相关，用于图像 XYDerivative 边缘检测。shader 源码如下：

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES GPUImage GPUImageXYDerivativeFilter
//@Time:2022/07/02 06:30
//@Motto:不积跬步无以至千里，不积小流无以成江海，程序人生的精彩需要坚持不懈地积累！
/******************************************************************************************/

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageGradientFragmentShaderString = SHADER_STRING
(
 precision highp 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 sampler2D inputImageTexture;

 uniform float edgeStrength;

 void main()
 {
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;

     float verticalDerivative = -topLeftIntensity - topIntensity - topRightIntensity + bottomLeftIntensity + bottomIntensity + bottomRightIntensity;
     float horizontalDerivative = -bottomLeftIntensity - leftIntensity - topLeftIntensity + bottomRightIntensity + rightIntensity + topRightIntensity;
     verticalDerivative = verticalDerivative * edgeStrength;
     horizontalDerivative = horizontalDerivative * edgeStrength;

     // Scaling the X * Y operation so that negative numbers are not clipped in the 0..1 range. This will be expanded in the corner detection filter
     gl_FragColor = vec4(horizontalDerivative * horizontalDerivative, verticalDerivative * verticalDerivative, ((verticalDerivative * horizontalDerivative) + 1.0) / 2.0, 1.0);
 }
);
#else
NSString *const kGPUImageGradientFragmentShaderString = SHADER_STRING
(
 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 sampler2D inputImageTexture;

 uniform float edgeStrength;

 void main()
 {
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;

     float verticalDerivative = -topLeftIntensity - topIntensity - topRightIntensity + bottomLeftIntensity + bottomIntensity + bottomRightIntensity;
     float horizontalDerivative = -bottomLeftIntensity - leftIntensity - topLeftIntensity + bottomRightIntensity + rightIntensity + topRightIntensity;
     verticalDerivative = verticalDerivative * edgeStrength;
     horizontalDerivative = horizontalDerivative * edgeStrength;

     // Scaling the X * Y operation so that negative numbers are not clipped in the 0..1 range. This will be expanded in the corner detection filter
     gl_FragColor = vec4(horizontalDerivative * horizontalDerivative, verticalDerivative * verticalDerivative, ((verticalDerivative * horizontalDerivative) + 1.0) / 2.0, 1.0);
 }
);
#endif