GPUImage--美颜滤镜GPUImageBeautifyFilter

关于GPUimage的介绍请看这里GPUImage:滤镜、美颜、视频流处理

美颜只是不同滤镜组合起来的效果，实际上美颜也是一种滤镜，它的需求较多，于是自称一派。

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GPUImageBeautifyFilter

/*
GPUImageBeautifyFilter是基于GPUImage的实时美颜滤镜中的美颜滤镜，包括GPUImageBilateralFilter、GPUImageCannyEdgeDetectionFilter、GPUImageCombinationFilter、GPUImageHSBFilter。
*/

在GPUImageBeautifyFilter.h中有：分别创建对应上面的对象

#import "GPUImage.h"

@class GPUImageCombinationFilter;

@interface GPUImageBeautifyFilter : GPUImageFilterGroup {
    GPUImageBilateralFilter *bilateralFilter;
    GPUImageCannyEdgeDetectionFilter *cannyEdgeFilter;
    GPUImageCombinationFilter *combinationFilter;
    GPUImageHSBFilter *hsbFilter;
}

@end

绘制流程分为：

1. 准备纹理
2. 绘制纹理
3. 显示处理后的纹理

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一、 准备纹理：这里用到的类
[GPUImageVideoCamera] -
[GPUImageBeautifyFilter] -
[GPUImageBilateralFliter] -
[GPUImageCombinationFilter] -
[GPUImageCannyEdgeDetectionFilter] -

准备 过程：

第一个纹理：
1、GPUImageVideoCamera捕获摄像头图像
调用newFrameReadyAtTime: atIndex:通知GPUImageBeautifyFilter；
2、GPUImageBeautifyFilter调用newFrameReadyAtTime: atIndex:
通知GPUImageBilateralFliter输入纹理已经准备好；
第二个纹理：
3、GPUImageBilateralFliter 绘制图像后，
informTargetsAboutNewFrameAtTime()，
调用setInputFramebufferForTarget: atIndex:
把绘制的图像设置为GPUImageCombinationFilter输入纹理，
并通知GPUImageCombinationFilter纹理已经绘制完毕；
4、GPUImageBeautifyFilter调用newFrameReadyAtTime: atIndex:
通知 GPUImageCannyEdgeDetectionFilter输入纹理已经准备好；
第三个纹理：
5、同3，GPUImageCannyEdgeDetectionFilter 绘制图像后，
把图像设置为GPUImageCombinationFilter输入纹理；
6、GPUImageBeautifyFilter调用newFrameReadyAtTime: atIndex:
通知 GPUImageCombinationFilter输入纹理已经准备好；

原文：http://blog.sina.com.cn/s/blog_61bc01360102wpl2.html

二、绘制纹理：

7、判断纹理数量
GPUImageCombinationFilter判断是否有三个纹理，三个纹理都已经准备好后
调用GPUImageThreeInputFilter的绘制函数renderToTextureWithVertices: textureCoordinates:，
图像绘制完后，把图像设置为GPUImageHSBFilter的输入纹理,
通知GPUImageHSBFilter纹理已经绘制完毕；
8、绘制纹理
GPUImageHSBFilter调用renderToTextureWithVertices:
textureCoordinates:绘制图像，
完成后把图像设置为GPUImageView的输入纹理，并通知GPUImageView输入纹理已经绘制完毕；

显示纹理

9、GPUImageView把输入纹理绘制到自己的帧缓存，然后通过
[self.context presentRenderbuffer:GL_RENDERBUFFER];显示到UIView上。

GPUImageBeautifyFilter.m文件是这样的

//
//  GPUImageBeautifyFilter.m
//  BeautifyFaceDemo
//
//  Created by guikz on 16/4/28.
//  Copyright © 2016年 guikz. All rights reserved.
//

#import "GPUImageBeautifyFilter.h"

// Internal CombinationFilter(It should not be used outside)
@interface GPUImageCombinationFilter : GPUImageThreeInputFilter
{
    GLint smoothDegreeUniform;
}

@property (nonatomic, assign) CGFloat intensity;

@end

NSString *const kGPUImageBeautifyFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 varying highp vec2 textureCoordinate2;
 varying highp vec2 textureCoordinate3;

 uniform sampler2D inputImageTexture;
 uniform sampler2D inputImageTexture2;
 uniform sampler2D inputImageTexture3;
 uniform mediump float smoothDegree;

 void main()
 {
     highp vec4 bilateral = texture2D(inputImageTexture, textureCoordinate);
     highp vec4 canny = texture2D(inputImageTexture2, textureCoordinate2);
     highp vec4 origin = texture2D(inputImageTexture3,textureCoordinate3);
     highp vec4 smooth;
     lowp float r = origin.r;
     lowp float g = origin.g;
     lowp float b = origin.b;
     if (canny.r < 0.2 && r > 0.3725 && g > 0.1568 && b > 0.0784 && r > b && (max(max(r, g), b) - min(min(r, g), b)) > 0.0588 && abs(r-g) > 0.0588) {
         smooth = (1.0 - smoothDegree) * (origin - bilateral) + bilateral;
     }
     else {
         smooth = origin;
     }
     smooth.r = log(1.0 + 0.2 * smooth.r)/log(1.2);
     smooth.g = log(1.0 + 0.2 * smooth.g)/log(1.2);
     smooth.b = log(1.0 + 0.2 * smooth.b)/log(1.2);
     gl_FragColor = smooth;
 }
 );

@implementation GPUImageCombinationFilter

- (id)init {
    if (self = [super initWithFragmentShaderFromString:kGPUImageBeautifyFragmentShaderString]) {
        smoothDegreeUniform = [filterProgram uniformIndex:@"smoothDegree"];
    }
    self.intensity = 0.5;
    return self;
}

- (void)setIntensity:(CGFloat)intensity {
    _intensity = intensity;
    [self setFloat:intensity forUniform:smoothDegreeUniform program:filterProgram];
}

@end

@implementation GPUImageBeautifyFilter

- (id)init;
{
    if (!(self = [super init]))
    {
        return nil;
    }

    // First pass: face smoothing filter
    bilateralFilter = [[GPUImageBilateralFilter alloc] init];
    bilateralFilter.distanceNormalizationFactor = 4.0;
    [self addFilter:bilateralFilter];

    // Second pass: edge detection
    cannyEdgeFilter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
    [self addFilter:cannyEdgeFilter];

    // Third pass: combination bilateral, edge detection and origin
    combinationFilter = [[GPUImageCombinationFilter alloc] init];
    [self addFilter:combinationFilter];

    // Adjust HSB
    hsbFilter = [[GPUImageHSBFilter alloc] init];
    [hsbFilter adjustBrightness:1.1];
    [hsbFilter adjustSaturation:1.1];

    [bilateralFilter addTarget:combinationFilter];
    [cannyEdgeFilter addTarget:combinationFilter];

    [combinationFilter addTarget:hsbFilter];

    self.initialFilters = [NSArray arrayWithObjects:bilateralFilter,cannyEdgeFilter,combinationFilter,nil];
    self.terminalFilter = hsbFilter;

    return self;
}


#pragma mark 绘制第一个纹理

- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
{
    for (GPUImageOutput *currentFilter in self.initialFilters)
    {
        if (currentFilter != self.inputFilterToIgnoreForUpdates)
        {
            if (currentFilter == combinationFilter) {
                textureIndex = 2;
            }
            [currentFilter newFrameReadyAtTime:frameTime atIndex:textureIndex];
        }
    }
}

- (void)setInputFramebuffer:(GPUImageFramebuffer *)newInputFramebuffer atIndex:(NSInteger)textureIndex;
{
    for (GPUImageOutput *currentFilter in self.initialFilters)
    {
        if (currentFilter == combinationFilter) {
            textureIndex = 2;
        }
        [currentFilter setInputFramebuffer:newInputFramebuffer atIndex:textureIndex];
    }
}

@end