iOS实现实时美颜滤镜并获取原图

实时美颜

在iOS里面进行实时美颜，我使用的是GPUImageBeautifyFilter, 具体原理可以看作者的文章。

具体使用方法如下：

1.在项目的`Podfile`里面引入`GPUImage`

target 'TestBeauty' do
    pod 'GPUImage'
end

2.将`GPUImageBeautyFilter.h`和`GPUImageBeautyFilter.m`添加到项目中

将GPUImageBeautyFilter添加到项目中

3.编写相关代码

在ViewController.m里面实现如下代码：

#import "ViewController.h"
#import <GPUImage/GPUImage.h>
#import "GPUImageBeautifyFilter.h"

@interface ViewController ()

@property (nonatomic, strong) GPUImageVideoCamera *videoCamera;
@property (nonatomic, strong) GPUImageView *filterView;
@end


@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];    
    // 设置使用前置摄像头进行美颜
    self.videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:AVCaptureDevicePositionFront];
    self.videoCamera.outputImageOrientation = UIInterfaceOrientationPortrait;
    self.videoCamera.horizontallyMirrorFrontFacingCamera = YES; // 镜像
    
    self.filterView = [[GPUImageView alloc] initWithFrame:self.view.frame];
    self.filterView.backgroundColor = [UIColor redColor];
    self.filterView.center = self.view.center;
    
    [self.view addSubview:self.filterView];
    [self.videoCamera addTarget:self.filterView];
    [self.videoCamera startCameraCapture];
}

运行项目之后，就可以成功实时美颜。

4.获取美颜之前的原图

如果想要获取美颜之前的原图，可以实现GPUImageVideoCameraDelegate协议里面的方法

需要进行如下修改：

@interface ViewController () <GPUImageVideoCameraDelegate>
在ViewController.m的viewDidLoad方法里面，让self.videoCamera.delegate = self;
实现协议里面的- (void)willOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer方法。将CMSampleBufferRef -> CVPixelBufferRef -> CGImage -> UIImage经过如下转换，获取到原图

通过下方这个方法，可以把CMSampleBufferRef转成UIImage，stackoverflow上有人已经给出了答案，代码如下

#define clamp(a) (a>255?255:(a<0?0:a))

- (UIImage *)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer {
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    uint8_t *yBuffer = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);
    size_t yPitch = CVPixelBufferGetBytesPerRowOfPlane(imageBuffer, 0);
    uint8_t *cbCrBuffer = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 1);
    size_t cbCrPitch = CVPixelBufferGetBytesPerRowOfPlane(imageBuffer, 1);
    
    int bytesPerPixel = 4;
    uint8_t *rgbBuffer = malloc(width * height * bytesPerPixel);
    
    for(int y = 0; y < height; y++) {
        uint8_t *rgbBufferLine = &rgbBuffer[y * width * bytesPerPixel];
        uint8_t *yBufferLine = &yBuffer[y * yPitch];
        uint8_t *cbCrBufferLine = &cbCrBuffer[(y >> 1) * cbCrPitch];
        
        for(int x = 0; x < width; x++) {
            int16_t y = yBufferLine[x];
            int16_t cb = cbCrBufferLine[x & ~1] - 128;
            int16_t cr = cbCrBufferLine[x | 1] - 128;
            
            uint8_t *rgbOutput = &rgbBufferLine[x*bytesPerPixel];
            
            int16_t r = (int16_t)roundf( y + cr *  1.4 );
            int16_t g = (int16_t)roundf( y + cb * -0.343 + cr * -0.711 );
            int16_t b = (int16_t)roundf( y + cb *  1.765);
            
            rgbOutput[0] = 0xff;
            rgbOutput[1] = clamp(b);
            rgbOutput[2] = clamp(g);
            rgbOutput[3] = clamp(r);
        }
    }
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(rgbBuffer, width, height, 8, width * bytesPerPixel, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    UIImage *image = [UIImage imageWithCGImage:quartzImage];
    
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    CGImageRelease(quartzImage);
    free(rgbBuffer);
    
    CVPixelBufferUnlockBaseAddress(imageBuffer, 0);
    
    return image;
}

经过以上几步，可以成功拿到未美颜的原图。但是需要注意图片的方向问题：图片的imageOrientation的值是0(即UIImageOrientationUp)，但是把图片发送到服务器打开一看，发现逆时针旋转了90度，而且镜像了。而且图片的宽和高的值对换了，比如说正常图片是宽480x高640，但是拿到的未美颜的图片是宽640X高480。

在镜头里看到的美颜后的人脸图片如下图所示：

美颜后

在协议方法willOutputSampleBuffer里面用上面这个imageFromSampleBuffer方法取出的未美颜的原图所如下所示：

未美颜

因为未美颜的原图的imageOrientation的值是0，不能直接使用我写的另一篇笔记：调用相机拍照图片旋转了90度里的方法一调整图片方向，但是调整的原理是一样的。

所以，在把未美颜的原图发送到服务器之前，需要将图片进行如下变换：

- (UIImage *)fixNotBeautyImageOrientation:(UIImage *)originImage {
    CGAffineTransform transform = CGAffineTransformIdentity;
    transform = CGAffineTransformTranslate(transform, originImage.size.height, 0);
    transform = CGAffineTransformRotate(transform, M_PI_2);
    transform = CGAffineTransformTranslate(transform, originImage.size.width, 0);
    transform = CGAffineTransformScale(transform, -1, 1);
    
    CGContextRef ctx = CGBitmapContextCreate(NULL, originImage.size.height, originImage.size.width,
                                             CGImageGetBitsPerComponent(originImage.CGImage), 0,
                                             CGImageGetColorSpace(originImage.CGImage),
                                             CGImageGetBitmapInfo(originImage.CGImage));
    CGContextConcatCTM(ctx, transform);
    CGContextDrawImage(ctx, CGRectMake( 0, 0,originImage.size.width,originImage.size.height), originImage.CGImage);
    
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    return img;
}

下面用图片来详细说一下是如何进行变换，最后得到正确的图片的：