iOS扫描二维码实现手势拉近拉远镜头

///记录开始的缩放比例@property(nonatomic,assign)CGFloat beginGestureScale;///最后的缩放比例@property(nonatomic,assign)CGFloat effectiveScale;- (void)cameraInitOver{ if (self.isVideoZoom) {  UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchDetected:)];  pinch.delegate = self;  [self.view addGestureRecognizer:pinch]; }}- (void)pinchDetected:(UIPinchGestureRecognizer*)recogniser{ self.effectiveScale = self.beginGestureScale * recogniser.scale; if (self.effectiveScale < 1.0){  self.effectiveScale = 1.0; } [self.scanObj setVideoScale:self.effectiveScale];}- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{ if ( [gestureRecognizer isKindOfClass:[UIPinchGestureRecognizer class]] ) {  _beginGestureScale = _effectiveScale; } return YES;}

- (void)setVideoScale:(CGFloat)scale{ [_input.device lockForConfiguration:nil]; AVCaptureConnection *videoConnection = [self connectionWithMediaType:AVMediaTypeVideo fromConnections:[[self stillImageOutput] connections]]; CGFloat maxScaleAndCropFactor = ([[self.stillImageOutput connectionWithMediaType:AVMediaTypeVideo] videoMaxScaleAndCropFactor])/16; if (scale > maxScaleAndCropFactor)  scale = maxScaleAndCropFactor; CGFloat zoom = scale / videoConnection.videoScaleAndCropFactor; videoConnection.videoScaleAndCropFactor = scale; [_input.device unlockForConfiguration]; CGAffineTransform transform = _videoPreView.transform; [CATransaction begin]; [CATransaction setAnimationDuration:.025];  _videoPreView.transform = CGAffineTransformScale(transform, zoom, zoom); [CATransaction commit];}