IOS OpenGL ES GPUImage 图像Lanczos重取样模糊效果 GPUImageLanczosResamplingFilter

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.

GPUImageLanczosResamplingFilter 属于 GPUImage 图像视觉效果相关，用来处理**图像 Lanczos 重取样模糊效果**。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 图像Lanczos重取样模糊效果 GPUImageLanczosResamplingFilter
//@Time:2022/06/11 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 kGPUImageLanczosFragmentShaderString = SHADER_STRING
(precision highp float;uniform sampler2D inputImageTexture;varying vec2 centerTextureCoordinate;varying vec2 oneStepLeftTextureCoordinate;varying vec2 twoStepsLeftTextureCoordinate;varying vec2 threeStepsLeftTextureCoordinate;varying vec2 fourStepsLeftTextureCoordinate;varying vec2 oneStepRightTextureCoordinate;varying vec2 twoStepsRightTextureCoordinate;varying vec2 threeStepsRightTextureCoordinate;varying vec2 fourStepsRightTextureCoordinate;// sinc(x) * sinc(x/a) = (a * sin(pi * x) * sin(pi * x / a)) / (pi^2 * x^2)// Assuming a Lanczos constant of 2.0, and scaling values to max out at x = +/- 1.5void main(){lowp vec4 fragmentColor = texture2D(inputImageTexture, centerTextureCoordinate) * 0.38026;fragmentColor += texture2D(inputImageTexture, oneStepLeftTextureCoordinate) * 0.27667;fragmentColor += texture2D(inputImageTexture, oneStepRightTextureCoordinate) * 0.27667;fragmentColor += texture2D(inputImageTexture, twoStepsLeftTextureCoordinate) * 0.08074;fragmentColor += texture2D(inputImageTexture, twoStepsRightTextureCoordinate) * 0.08074;fragmentColor += texture2D(inputImageTexture, threeStepsLeftTextureCoordinate) * -0.02612;fragmentColor += texture2D(inputImageTexture, threeStepsRightTextureCoordinate) * -0.02612;fragmentColor += texture2D(inputImageTexture, fourStepsLeftTextureCoordinate) * -0.02143;fragmentColor += texture2D(inputImageTexture, fourStepsRightTextureCoordinate) * -0.02143;gl_FragColor = fragmentColor;}
);
#else
NSString *const kGPUImageLanczosFragmentShaderString = SHADER_STRING
(uniform sampler2D inputImageTexture;varying vec2 centerTextureCoordinate;varying vec2 oneStepLeftTextureCoordinate;varying vec2 twoStepsLeftTextureCoordinate;varying vec2 threeStepsLeftTextureCoordinate;varying vec2 fourStepsLeftTextureCoordinate;varying vec2 oneStepRightTextureCoordinate;varying vec2 twoStepsRightTextureCoordinate;varying vec2 threeStepsRightTextureCoordinate;varying vec2 fourStepsRightTextureCoordinate;// sinc(x) * sinc(x/a) = (a * sin(pi * x) * sin(pi * x / a)) / (pi^2 * x^2)// Assuming a Lanczos constant of 2.0, and scaling values to max out at x = +/- 1.5void main(){vec4 fragmentColor = texture2D(inputImageTexture, centerTextureCoordinate) * 0.38026;fragmentColor += texture2D(inputImageTexture, oneStepLeftTextureCoordinate) * 0.27667;fragmentColor += texture2D(inputImageTexture, oneStepRightTextureCoordinate) * 0.27667;fragmentColor += texture2D(inputImageTexture, twoStepsLeftTextureCoordinate) * 0.08074;fragmentColor += texture2D(inputImageTexture, twoStepsRightTextureCoordinate) * 0.08074;fragmentColor += texture2D(inputImageTexture, threeStepsLeftTextureCoordinate) * -0.02612;fragmentColor += texture2D(inputImageTexture, threeStepsRightTextureCoordinate) * -0.02612;fragmentColor += texture2D(inputImageTexture, fourStepsLeftTextureCoordinate) * -0.02143;fragmentColor += texture2D(inputImageTexture, fourStepsRightTextureCoordinate) * -0.02143;gl_FragColor = fragmentColor;}
);
#endif