GPUImage – 调节图像颜色 GPUImageToneCurveFilter

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//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:GPUImage – 调节图像颜色 GPUImageToneCurveFilter
//@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！
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#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageToneCurveFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 uniform sampler2D inputImageTexture;
 uniform sampler2D toneCurveTexture;

 void main()
 {
     lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     lowp float redCurveValue = texture2D(toneCurveTexture, vec2(textureColor.r, 0.0)).r;
     lowp float greenCurveValue = texture2D(toneCurveTexture, vec2(textureColor.g, 0.0)).g;
     lowp float blueCurveValue = texture2D(toneCurveTexture, vec2(textureColor.b, 0.0)).b;

     gl_FragColor = vec4(redCurveValue, greenCurveValue, blueCurveValue, textureColor.a);
 }
);
#else
NSString *const kGPUImageToneCurveFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;
 uniform sampler2D inputImageTexture;
 uniform sampler2D toneCurveTexture;

 void main()
 {
     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     float redCurveValue = texture2D(toneCurveTexture, vec2(textureColor.r, 0.0)).r;
     float greenCurveValue = texture2D(toneCurveTexture, vec2(textureColor.g, 0.0)).g;
     float blueCurveValue = texture2D(toneCurveTexture, vec2(textureColor.b, 0.0)).b;

     gl_FragColor = vec4(redCurveValue, greenCurveValue, blueCurveValue, textureColor.a);
 }
);
#endif