IOS – OpenGL ES 设置图像模糊 GPUImageFastBlurFilter

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//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 设置图像模糊 GPUImageFastBlurFilter
//@Time:2022/04/22 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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attribute vec4 position;
attribute vec2 inputTextureCoordinate;
uniform highp float texelWidthOffset;
uniform highp float texelHeightOffset;
uniform highp float blurSize;
varying highp vec2 centerTextureCoordinate;
varying highp vec2 oneStepLeftTextureCoordinate;
varying highp vec2 twoStepsLeftTextureCoordinate;
varying highp vec2 oneStepRightTextureCoordinate;
varying highp vec2 twoStepsRightTextureCoordinate;
// const float offset[3] = float[]( 0.0, 1.3846153846, 3.2307692308 );
void main()
{
    gl_Position = position;
    vec2 firstOffset = vec2(1.3846153846 * texelWidthOffset, 1.3846153846 * texelHeightOffset) * blurSize;
    vec2 secondOffset = vec2(3.2307692308 * texelWidthOffset, 3.2307692308 * texelHeightOffset) * blurSize;
    centerTextureCoordinate = inputTextureCoordinate;
    oneStepLeftTextureCoordinate = inputTextureCoordinate - firstOffset;
    twoStepsLeftTextureCoordinate = inputTextureCoordinate - secondOffset;
    oneStepRightTextureCoordinate = inputTextureCoordinate + firstOffset;
    twoStepsRightTextureCoordinate = inputTextureCoordinate + secondOffset;
}




precision highp float;
uniform sampler2D inputImageTexture;
varying highp vec2 centerTextureCoordinate;
varying highp vec2 oneStepLeftTextureCoordinate;
varying highp vec2 twoStepsLeftTextureCoordinate;
n varying highp vec2 oneStepRightTextureCoordinate;
varying highp vec2 twoStepsRightTextureCoordinate;
// const float weight[3] = float[]( 0.2270270270, 0.3162162162, 0.0702702703 );
void main()
{
    lowp vec4 fragmentColor = texture2D(inputImageTexture, centerTextureCoordinate) * 0.2270270270;
    fragmentColor += texture2D(inputImageTexture, oneStepLeftTextureCoordinate) * 0.3162162162;
    fragmentColor += texture2D(inputImageTexture, oneStepRightTextureCoordinate) * 0.3162162162;
    fragmentColor += texture2D(inputImageTexture, twoStepsLeftTextureCoordinate) * 0.0702702703;
    fragmentColor += texture2D(inputImageTexture, twoStepsRightTextureCoordinate) * 0.0702702703;
    gl_FragColor = fragmentColor;
}