GPUImage – 亮度平均 GPUImageLuminosity-猿说编程

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零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES GPUImage 使用
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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.

GPUImageLuminosity 属于 GPUImage 颜色处理相关，用来处理图片亮度平均，像 GPUImageAverageColor 一样，将图像缩小到其平均亮度。

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:GPUImage – 亮度平均 GPUImageLuminosity
//@Time:2022/03/25 07:30
//@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 kGPUImageInitialLuminosityFragmentShaderString = SHADER_STRING
(
 precision highp float;
 
 uniform sampler2D inputImageTexture;
 
 varying highp vec2 outputTextureCoordinate;
 
 varying highp vec2 upperLeftInputTextureCoordinate;
 varying highp vec2 upperRightInputTextureCoordinate;
 varying highp vec2 lowerLeftInputTextureCoordinate;
 varying highp vec2 lowerRightInputTextureCoordinate;
 
 const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);

 void main()
 {
     highp float upperLeftLuminance = dot(texture2D(inputImageTexture, upperLeftInputTextureCoordinate).rgb, W);
     highp float upperRightLuminance = dot(texture2D(inputImageTexture, upperRightInputTextureCoordinate).rgb, W);
     highp float lowerLeftLuminance = dot(texture2D(inputImageTexture, lowerLeftInputTextureCoordinate).rgb, W);
     highp float lowerRightLuminance = dot(texture2D(inputImageTexture, lowerRightInputTextureCoordinate).rgb, W);

     highp float luminosity = 0.25 * (upperLeftLuminance + upperRightLuminance + lowerLeftLuminance + lowerRightLuminance);
     gl_FragColor = vec4(luminosity, luminosity, luminosity, 1.0);
 }
);

NSString *const kGPUImageLuminosityFragmentShaderString = SHADER_STRING
(
 precision highp float;
 
 uniform sampler2D inputImageTexture;
 
 varying highp vec2 outputTextureCoordinate;
 
 varying highp vec2 upperLeftInputTextureCoordinate;
 varying highp vec2 upperRightInputTextureCoordinate;
 varying highp vec2 lowerLeftInputTextureCoordinate;
 varying highp vec2 lowerRightInputTextureCoordinate;
 
 void main()
 {
     highp float upperLeftLuminance = texture2D(inputImageTexture, upperLeftInputTextureCoordinate).r;
     highp float upperRightLuminance = texture2D(inputImageTexture, upperRightInputTextureCoordinate).r;
     highp float lowerLeftLuminance = texture2D(inputImageTexture, lowerLeftInputTextureCoordinate).r;
     highp float lowerRightLuminance = texture2D(inputImageTexture, lowerRightInputTextureCoordinate).r;
     
     highp float luminosity = 0.25 * (upperLeftLuminance + upperRightLuminance + lowerLeftLuminance + lowerRightLuminance);
     gl_FragColor = vec4(luminosity, luminosity, luminosity, 1.0);
 }
);
#else
NSString *const kGPUImageInitialLuminosityFragmentShaderString = SHADER_STRING
(
 uniform sampler2D inputImageTexture;
 
 varying vec2 outputTextureCoordinate;
 
 varying vec2 upperLeftInputTextureCoordinate;
 varying vec2 upperRightInputTextureCoordinate;
 varying vec2 lowerLeftInputTextureCoordinate;
 varying vec2 lowerRightInputTextureCoordinate;
 
 const vec3 W = vec3(0.2125, 0.7154, 0.0721);
 
 void main()
 {
     float upperLeftLuminance = dot(texture2D(inputImageTexture, upperLeftInputTextureCoordinate).rgb, W);
     float upperRightLuminance = dot(texture2D(inputImageTexture, upperRightInputTextureCoordinate).rgb, W);
     float lowerLeftLuminance = dot(texture2D(inputImageTexture, lowerLeftInputTextureCoordinate).rgb, W);
     float lowerRightLuminance = dot(texture2D(inputImageTexture, lowerRightInputTextureCoordinate).rgb, W);
     
     float luminosity = 0.25 * (upperLeftLuminance + upperRightLuminance + lowerLeftLuminance + lowerRightLuminance);
     gl_FragColor = vec4(luminosity, luminosity, luminosity, 1.0);
 }
);

NSString *const kGPUImageLuminosityFragmentShaderString = SHADER_STRING
(
 uniform sampler2D inputImageTexture;
 
 varying vec2 outputTextureCoordinate;
 
 varying vec2 upperLeftInputTextureCoordinate;
 varying vec2 upperRightInputTextureCoordinate;
 varying vec2 lowerLeftInputTextureCoordinate;
 varying vec2 lowerRightInputTextureCoordinate;
 
 void main()
 {
     float upperLeftLuminance = texture2D(inputImageTexture, upperLeftInputTextureCoordinate).r;
     float upperRightLuminance = texture2D(inputImageTexture, upperRightInputTextureCoordinate).r;
     float lowerLeftLuminance = texture2D(inputImageTexture, lowerLeftInputTextureCoordinate).r;
     float lowerRightLuminance = texture2D(inputImageTexture, lowerRightInputTextureCoordinate).r;
     
     float luminosity = 0.25 * (upperLeftLuminance + upperRightLuminance + lowerLeftLuminance + lowerRightLuminance);
     gl_FragColor = vec4(luminosity, luminosity, luminosity, 1.0);
 }
);
#endif