AVCapture中实现拉近拉远镜头

这段代码在我机器上运行貌似一直出错，我后来是这样写的：

//写了这几句话 貌似远点了  1224日

        [self.captureSession beginConfiguration];

        self.device.videoZoomFactor = 50.0f;

        AVCaptureStillImageOutput* output = (AVCaptureStillImageOutput*)[self.captureSession.outputs objectAtIndex:0];

        AVCaptureConnection *videoConnection = [output connectionWithMediaType:AVMediaTypeVideo];

        CGFloat maxScale = videoConnection.videoMaxScaleAndCropFactor;

        CGFloat zoom = maxScale / 50;

//        videoConnection.videoScaleAndCropFactor -= zoom;

        videoConnection.videoScaleAndCropFactor = 1.0f;

        [self.captureSession commitConfiguration];

转载自：http://blog.csdn.net/song_yu_tao/article/details/17305601

自己用avcapture实现自定制相机，系统相机是可以拉近拉远镜头的，网上搜寻了半天始终没有发现，刚才又翻看了半天的api接口，终于找到了，原来他藏在AVCaptureConnection中，videoScaleAndCropFactor：缩放裁剪系数。简单写了下使用方法：

 AVCaptureStillImageOutput* output = (AVCaptureStillImageOutput*)[self.captureSession.outputs objectAtIndex:0];
 AVCaptureConnection *videoConnection = [output connectionWithMediaType:AVMediaTypeVideo];
 CGFloat maxScale = videoConnection.videoMaxScaleAndCropFactor;
 CGFloat zoom = maxScale / 50;
 videoConnection.videoScaleAndCropFactor += zoom;
 self.preVideoView.transform = CGAffineTransformScale(self.preVideoView.transform, zoom, zoom);

其中preVideoView的layer中添加了AVCaptureVideoPreviewLayer。