CameraView 开始缩放级别

Question

哟！

我正在通过 objc 构建一个 CameraView，并找到了一些代码（复制意大利面）以使其与捏缩放一起使用。

我现在错过了如何编码/定义相机的缩放级别起点（无需用户捏）。

我希望它以至少 2 倍变焦开始。 我对有关相机和变焦的一切都不熟悉：D

这是我当前的代码的样子：

@property (nonatomic) AVCaptureDevice *camDevice;
@property (nonatomic) CGFloat zoomBegin;
@property (nonatomic) CGFloat zoomMax;

- (void)setupBackCamera {
    self.captureSession = [AVCaptureSession new];
    self.captureSession.sessionPreset = AVCaptureSessionPresetPhoto;
    AVCaptureDevice *backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (!backCamera) {
        NSLog(@"Unable to access back camera!");
        return;
    }
    
    NSError *error;
    
    //New Code
    // Manange camera In/Out
    if(YES == [backCamera lockForConfiguration:&error]) {        
        _zoomMax = backCamera.activeFormat.videoMaxZoomFactor;
        [backCamera unlockForConfiguration];
    }
    _camDevice = backCamera;
    [_previewView addGestureRecognizer: [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchToZoom:)]];
    
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:backCamera
                                                                        error:&error];
bla bla bla....

和....

- (void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer {
    /*CGFloat scale = pinchRecognizer.scale;
    self.imgFullCamera.transform = CGAffineTransformScale(self.imgFullCamera.transform, scale, scale);
    pinchRecognizer.scale = 1.0;
    */
    
    CGFloat lastScale = pinchRecognizer.scale;
    
    const CGFloat kMaxScale = 2.0;
    const CGFloat kMinScale = 1.0;
    CGFloat currentScale = [[[pinchRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];
    CGFloat newScale = 1 -  (lastScale - [pinchRecognizer scale]);
    newScale = MIN(newScale, kMaxScale / currentScale);
    newScale = MAX(newScale, kMinScale / currentScale);
    
    CGAffineTransform transform = CGAffineTransformScale(self.imgFullCamera.transform, newScale, newScale);
    self.imgFullCamera.transform = transform;
    
    pinchRecognizer.scale = newScale;
}

// MARK: - Manange zoom In/Out
- (void)pinchToZoom:(UIPinchGestureRecognizer*)gesture {
    switch (gesture.state) {
        case UIGestureRecognizerStateBegan:
            _zoomBegin = _camDevice.videoZoomFactor;
            NSLog(@"zoom begin:%.3f", _zoomBegin);
            break;
            
        case UIGestureRecognizerStateChanged:
        {
            CGFloat zoomTo = _zoomBegin + (gesture.scale * 2 - 2);
            
            // step 0.01 between 1.0 and zoomMax (4x on iPhone 6s)
            int msc = (int)(((zoomTo+0.001)*100))%100;
            zoomTo = (NSInteger)zoomTo + msc * 0.01;
            zoomTo = fmaxf(1, fminf(zoomTo, _zoomMax));
            
            if (_camDevice.videoZoomFactor != zoomTo) {
                //NSLog(@"zoom changed:%.3f", zoomTo);
                dispatch_async(dispatch_get_main_queue(), ^{
                    NSError *error;
                    if ( YES == [self->_camDevice lockForConfiguration:&error]) {
                        self->_camDevice.videoZoomFactor = zoomTo;
                        [self->_camDevice unlockForConfiguration];
                        NSLog(@"zoom changed: %.3f", zoomTo);
                    }
                });
            }
            break;
        }
            
        default:
            break;
    }
}

谢谢