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

2022/7/7 6:20:17

编程Tag： 图像 ios es OpenGL fragmentColor inputImageTexture GPUImageLanczosResamplingFilter

本文主要是介绍IOS OpenGL ES GPUImage 图像Lanczos重取样模糊效果 GPUImageLanczosResamplingFilter，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

一.简介
二.效果演示
三.源码下载
四.猜你喜欢

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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 = +/- 1.5

 void 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 = +/- 1.5

 void 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