iOS给一张照片美颜

之前我的一篇笔记iOS实时美颜并获取原图里面写了如何实现实时的美颜滤镜，本篇作为补充说下如何给一张图片美颜。

还是使用之前提到的GPUImageBeautifyFilter

	// 原图
	UIImage * sourceImage = [UIImage imageNamed:@"notBeauty.png"];

    GPUImageBeautifyFilter *beautyFilter = [[GPUImageBeautifyFilter alloc] init];
    //设置要渲染的区域
    [beautyFilter forceProcessingAtSize:sourceImage.size];
    [beautyFilter useNextFrameForImageCapture];
    //获取数据源
    GPUImagePicture *stillImageSource = [[GPUImagePicture alloc]initWithImage:sourceImage];
    //添加上滤镜
    [stillImageSource addTarget:beautyFilter];
    //开始渲染
    [stillImageSource processImage];
    //获取滤镜后的图片
    UIImage *beautyImage = [beautyFilter imageFromCurrentFramebuffer];
    [beautyFilter removeAllTargets];
    [stillImageSource removeAllTargets];

根据以上代码，UIImage *beautyImage存储的就是美颜后的图片。

上面写的是如何把一个图片美颜，下面说下如何使用GPUImage实现一个美颜相机 。

看如下示例代码

- (void)viewDidLoad {
    [super viewDidLoad];

    CGRect mainScreenFrame = [[UIScreen mainScreen] bounds];
	GPUImageView *primaryView = [[GPUImageView alloc] initWithFrame:mainScreenFrame];
    primaryView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

    self.takePhotoButton = [[UIButton alloc] initWithFrame:CGRectMake([UIScreen mainScreen].bounds.size.width/2 - 25, [UIScreen mainScreen].bounds.size.height - 60, 50, 50)];
    [self.takePhotoButton setTitle:@"拍照" forState:UIControlStateNormal];
    self.takePhotoButton.backgroundColor = [UIColor clearColor];
    [self.takePhotoButton setTitleColor:[UIColor blueColor] forState:UIControlStateNormal];
    [self.takePhotoButton addTarget:self action:@selector(takePhotoButtonClicked) forControlEvents:UIControlEventTouchUpInside];
    [primaryView addSubview:self.takePhotoButton];

	self.view = primaryView;
	self.cameraPosition = AVCaptureDevicePositionBack;
	[self initCameraAndFilterWithPosition:self.cameraPosition];
}

// 初始化美颜相机
- (void)initCameraAndFilterWithPosition:(AVCaptureDevicePosition)position {
    self.stillCamera = [[GPUImageStillCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:position];
    self.stillCamera.outputImageOrientation = UIInterfaceOrientationPortrait;
    if (AVCaptureDevicePositionFront == position) {
        // 前置摄像头，镜像展示
        self.stillCamera.horizontallyMirrorFrontFacingCamera = YES;
    }
    self.beautyFilter = [[GPUImageBeautifyFilter alloc] init];
    [self.stillCamera addTarget:self.beautyFilter];
    GPUImageView * filterView = (GPUImageView *)self.view;
    [self.beautyFilter addTarget:filterView];
    [self.stillCamera startCameraCapture];
}


// 点击了拍照按钮
- (void)takePhotoButtonClicked {
    [self.stillCamera capturePhotoAsJPEGProcessedUpToFilter:self.beautyFilter withCompletionHandler:^(NSData *processedJPEG, NSError *error){
        
        __weak typeof(self) weakSelf = self;
        dispatch_async(dispatch_get_main_queue(), ^{
        	// 获取美颜过的相片
        	UIImage * beautyPhoto = [UIImage imageWithData:processedJPEG];

            // ……
            // ……
        });
    }];
}

如果要获取未美颜的原图，可以参照我上一篇笔记iOS实时美颜滤镜并获取原图里面的方法原理获取原图。即实现GPUImageVideoCameraDelegate协议里面的方法- (void)willOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer。

这里有个需要注意的点：使用GPUImage的前置摄像头与后置摄像头获取到的原图方向不是一样的，可能是因为前置摄像头的时候设置了horizontallyMirrorFrontFacingCamera = YES的原因。

• 使用前置摄像头获取到的原图，orientation是0，但是相当于leftMirror了
• 使用后置摄像头获取到的原图，orientation是0，但是相当于left了

所以，如果使用后置摄像头拍照，获取未美颜的原图的时候，转换代码如下：

- (UIImage *)fixNotBeautyImageOrientation:(UIImage *)originImage {
    CGAffineTransform transform = CGAffineTransformIdentity;
    
    transform = CGAffineTransformRotate(transform, -M_PI_2);
    transform = CGAffineTransformTranslate(transform, - originImage.size.width, 0);

    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;
}