IOS – OpenGL ES 图像加亮边缘 GPUImage3x3ConvolutionFilter

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一.简介
二.效果演示
三.源码下载
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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.

GPUImage3x3ConvolutionFilter 属于 GPUImage 图像视觉效果相关，用来处理图像加亮边缘。shader 源码如下：

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 图像加亮边缘 GPUImage3x3ConvolutionFilter
//@Time:2022/06/08 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 kGPUImage3x3ConvolutionFragmentShaderString = SHADER_STRING
(
 precision highp float;

 uniform sampler2D inputImageTexture;

 uniform mediump mat3 convolutionMatrix;

 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;

 void main()
 {
     mediump vec3 bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
     mediump vec3 bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).rgb;
     mediump vec3 bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).rgb;
     mediump vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);
     mediump vec3 leftColor = texture2D(inputImageTexture, leftTextureCoordinate).rgb;
     mediump vec3 rightColor = texture2D(inputImageTexture, rightTextureCoordinate).rgb;
     mediump vec3 topColor = texture2D(inputImageTexture, topTextureCoordinate).rgb;
     mediump vec3 topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).rgb;
     mediump vec3 topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).rgb;

     mediump vec3 resultColor = topLeftColor * convolutionMatrix[0][0] + topColor * convolutionMatrix[0][1] + topRightColor * convolutionMatrix[0][2];
     resultColor += leftColor * convolutionMatrix[1][0] + centerColor.rgb * convolutionMatrix[1][1] + rightColor * convolutionMatrix[1][2];
     resultColor += bottomLeftColor * convolutionMatrix[2][0] + bottomColor * convolutionMatrix[2][1] + bottomRightColor * convolutionMatrix[2][2];

     gl_FragColor = vec4(resultColor, centerColor.a);
 }
);
#else
NSString *const kGPUImage3x3ConvolutionFragmentShaderString = SHADER_STRING
(
 uniform sampler2D inputImageTexture;

 uniform mat3 convolutionMatrix;

 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;

 void main()
 {
     vec3 bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).rgb;
     vec3 bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).rgb;
     vec3 bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).rgb;
     vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);
     vec3 leftColor = texture2D(inputImageTexture, leftTextureCoordinate).rgb;
     vec3 rightColor = texture2D(inputImageTexture, rightTextureCoordinate).rgb;
     vec3 topColor = texture2D(inputImageTexture, topTextureCoordinate).rgb;
     vec3 topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).rgb;
     vec3 topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).rgb;

     vec3 resultColor = topLeftColor * convolutionMatrix[0][0] + topColor * convolutionMatrix[0][1] + topRightColor * convolutionMatrix[0][2];
     resultColor += leftColor * convolutionMatrix[1][0] + centerColor.rgb * convolutionMatrix[1][1] + rightColor * convolutionMatrix[1][2];
     resultColor += bottomLeftColor * convolutionMatrix[2][0] + bottomColor * convolutionMatrix[2][1] + bottomRightColor * convolutionMatrix[2][2];

     gl_FragColor = vec4(resultColor, centerColor.a);
 }
);
#endif