IOS – OpenGL ES 调节图像色度 GPUImageHueFilter

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.

GPUImageHueFilter 属于 GPUImage 颜色处理相关，用来处理图片色度, **色调角度，以度为单位，默认为 90 度，**shader 源码如下：

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 调节图像色度 GPUImageHueFilter
//@Time:2022/04/01 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 kGPUImageHueFragmentShaderString = SHADER_STRING
(precision highp float;varying highp vec2 textureCoordinate;uniform sampler2D inputImageTexture;uniform mediump float hueAdjust;const highp  vec4  kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);const highp  vec4  kRGBToI     = vec4 (0.595716, -0.274453, -0.321263, 0.0);const highp  vec4  kRGBToQ     = vec4 (0.211456, -0.522591, 0.31135, 0.0);const highp  vec4  kYIQToR   = vec4 (1.0, 0.9563, 0.6210, 0.0);const highp  vec4  kYIQToG   = vec4 (1.0, -0.2721, -0.6474, 0.0);const highp  vec4  kYIQToB   = vec4 (1.0, -1.1070, 1.7046, 0.0);void main (){// Sample the input pixelhighp vec4 color   = texture2D(inputImageTexture, textureCoordinate);// Convert to YIQhighp float   YPrime  = dot (color, kRGBToYPrime);highp float   I      = dot (color, kRGBToI);highp float   Q      = dot (color, kRGBToQ);// Calculate the hue and chromahighp float   hue     = atan (Q, I);highp float   chroma  = sqrt (I * I + Q * Q);// Make the user's adjustmentshue += (-hueAdjust); //why negative rotation?// Convert back to YIQQ = chroma * sin (hue);I = chroma * cos (hue);// Convert back to RGBhighp vec4    yIQ   = vec4 (YPrime, I, Q, 0.0);color.r = dot (yIQ, kYIQToR);color.g = dot (yIQ, kYIQToG);color.b = dot (yIQ, kYIQToB);// Save the resultgl_FragColor = color;}
);
#else
NSString *const kGPUImageHueFragmentShaderString = SHADER_STRING
(varying vec2 textureCoordinate;uniform sampler2D inputImageTexture;uniform float hueAdjust;const vec4  kRGBToYPrime = vec4 (0.299, 0.587, 0.114, 0.0);const vec4  kRGBToI     = vec4 (0.595716, -0.274453, -0.321263, 0.0);const vec4  kRGBToQ     = vec4 (0.211456, -0.522591, 0.31135, 0.0);const vec4  kYIQToR   = vec4 (1.0, 0.9563, 0.6210, 0.0);const vec4  kYIQToG   = vec4 (1.0, -0.2721, -0.6474, 0.0);const vec4  kYIQToB   = vec4 (1.0, -1.1070, 1.7046, 0.0);void main (){// Sample the input pixelvec4 color   = texture2D(inputImageTexture, textureCoordinate);// Convert to YIQfloat   YPrime  = dot (color, kRGBToYPrime);float   I      = dot (color, kRGBToI);float   Q      = dot (color, kRGBToQ);// Calculate the hue and chromafloat   hue     = atan (Q, I);float   chroma  = sqrt (I * I + Q * Q);// Make the user's adjustmentshue += (-hueAdjust); //why negative rotation?// Convert back to YIQQ = chroma * sin (hue);I = chroma * cos (hue);// Convert back to RGBvec4    yIQ   = vec4 (YPrime, I, Q, 0.0);color.r = dot (yIQ, kYIQToR);color.g = dot (yIQ, kYIQToG);color.b = dot (yIQ, kYIQToB);// Save the resultgl_FragColor = color;}
);
#endif