IOS – OpenGL ES 调节图像灰色 GPUImageGrayscaleFilter

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//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 调节图像灰色 GPUImageGrayscaleFilter
//@Time:2022/03/16 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！
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageLuminanceFragmentShaderString = SHADER_STRING
(
 precision highp float;

 varying vec2 textureCoordinate;

 uniform sampler2D inputImageTexture;

 const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);

 void main()
 {
     lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     float luminance = dot(textureColor.rgb, W);

     gl_FragColor = vec4(vec3(luminance), textureColor.a);
 }
);
#else
NSString *const kGPUImageLuminanceFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;

 uniform sampler2D inputImageTexture;

 const vec3 W = vec3(0.2125, 0.7154, 0.0721);

 void main()
 {
     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     float luminance = dot(textureColor.rgb, W);

     gl_FragColor = vec4(vec3(luminance), textureColor.a);
 }
);
#endif