IOS – OpenGL ES 调节图像单色 GPUImageMonochromeFilter

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猿说编程[Python和C]

发布于 2023-03-23 07:37:39

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发布于 2023-03-23 07:37:39

文章被收录于专栏：猿说编程

零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 基础零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 转场零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 特效零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 函数零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES GPUImage 使用零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES GLSL 编程

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.

GPUImageMonochromeFilter 属于 GPUImage 颜色处理相关，用来处理图片单色，shader 源码如下：

/********************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 调节图像单色 GPUImageMonochromeFilter
//@Time:2022/03/18 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！
/******************************************************************************************/


#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUMonochromeFragmentShaderString = SHADER_STRING
(
 precision lowp float;

 varying highp vec2 textureCoordinate;

 uniform sampler2D inputImageTexture;
 uniform float intensity;
 uniform vec3 filterColor;

 const mediump vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);

 void main()
 {
    //desat, then apply overlay blend
    lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
    float luminance = dot(textureColor.rgb, luminanceWeighting);

    lowp vec4 desat = vec4(vec3(luminance), 1.0);

    //overlay
    lowp vec4 outputColor = vec4(
                                 (desat.r < 0.5 ? (2.0 * desat.r * filterColor.r) : (1.0 - 2.0 * (1.0 - desat.r) * (1.0 - filterColor.r))),
                                 (desat.g < 0.5 ? (2.0 * desat.g * filterColor.g) : (1.0 - 2.0 * (1.0 - desat.g) * (1.0 - filterColor.g))),
                                 (desat.b < 0.5 ? (2.0 * desat.b * filterColor.b) : (1.0 - 2.0 * (1.0 - desat.b) * (1.0 - filterColor.b))),
                                 1.0
                                 );

    //which is better, or are they equal?
    gl_FragColor = vec4( mix(textureColor.rgb, outputColor.rgb, intensity), textureColor.a);
 }
);
#else
NSString *const kGPUMonochromeFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;

 uniform sampler2D inputImageTexture;
 uniform float intensity;
 uniform vec3 filterColor;

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

 void main()
 {
     //desat, then apply overlay blend
     vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
     float luminance = dot(textureColor.rgb, luminanceWeighting);

     vec4 desat = vec4(vec3(luminance), 1.0);

     //overlay
     vec4 outputColor = vec4(
                                  (desat.r < 0.5 ? (2.0 * desat.r * filterColor.r) : (1.0 - 2.0 * (1.0 - desat.r) * (1.0 - filterColor.r))),
                                  (desat.g < 0.5 ? (2.0 * desat.g * filterColor.g) : (1.0 - 2.0 * (1.0 - desat.g) * (1.0 - filterColor.g))),
                                  (desat.b < 0.5 ? (2.0 * desat.b * filterColor.b) : (1.0 - 2.0 * (1.0 - desat.b) * (1.0 - filterColor.b))),
                                  1.0
                                  );

     //which is better, or are they equal?
     gl_FragColor = vec4( mix(textureColor.rgb, outputColor.rgb, intensity), textureColor.a);
 }
);
#endif