iphone - 如何从 UIImageView 获取全分辨率的旋转、缩放和平移图像？

Question

我有一个 UIImageView，可以使用手势识别器进行旋转、平移和缩放。结果，它在其封闭 View 中被裁剪。一切工作正常，但我不知道如何以全分辨率保存图片的可见部分。这不是屏幕抓取。

我知道我直接从 UIImageView 的可见内容获取 UIImage，但它仅限于屏幕的分辨率。

我假设我必须对 UIImage 进行相同的转换并裁剪它。有没有简单的方法可以做到这一点？

更新:例如，我有一个带有高分辨率图像的 UIImageView，比如说一张 8MP iPhone 4s 相机照片，它通过手势进行转换，因此它可以在其封闭 View 中缩放、旋转和移动。显然，正在进行一些裁剪，因此仅显示图像的一部分。显示的屏幕分辨率和下划线图像分辨率之间存在巨大差异，我需要图像分辨率中的图像。 UIImageView 位于 UIViewContentModeScaleAspectFit 中，但使用 UIViewContentModeScaleAspectFill 的解决方案也可以。

这是我的代码:

- (void)rotatePiece:(UIRotationGestureRecognizer *)gestureRecognizer {

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {
        [gestureRecognizer view].transform = CGAffineTransformRotate([[gestureRecognizer view] transform], [gestureRecognizer rotation]);
        [gestureRecognizer setRotation:0];
    }
}

- (void)scalePiece:(UIPinchGestureRecognizer *)gestureRecognizer {

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {
        [gestureRecognizer view].transform = CGAffineTransformScale([[gestureRecognizer view] transform], [gestureRecognizer scale], [gestureRecognizer scale]);
        [gestureRecognizer setScale:1];
    }
}

-(void)panGestureMoveAround:(UIPanGestureRecognizer *)gestureRecognizer;
{
    UIView *piece = [gestureRecognizer view];

    //We pass in the gesture to a method that will help us align our touches so that the pan and pinch will seems to originate between the fingers instead of other points or center point of the UIView    
    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {

        CGPoint translation = [gestureRecognizer translationInView:[piece superview]];
        [piece setCenter:CGPointMake([piece center].x + translation.x, [piece center].y+translation.y)];
        [gestureRecognizer setTranslation:CGPointZero inView:[piece superview]];
    } else if([gestureRecognizer state] == UIGestureRecognizerStateEnded) {
        //Put the code that you may want to execute when the UIView became larger than certain value or just to reset them back to their original transform scale
    }
}


- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    // if the gesture recognizers are on different views, don't allow simultaneous recognition
    if (gestureRecognizer.view != otherGestureRecognizer.view)
        return NO;

    // if either of the gesture recognizers is the long press, don't allow simultaneous recognition
    if ([gestureRecognizer isKindOfClass:[UILongPressGestureRecognizer class]] || [otherGestureRecognizer isKindOfClass:[UILongPressGestureRecognizer class]])
        return NO;

    return YES;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];    
    faceImageView.image = appDelegate.faceImage;

    UIRotationGestureRecognizer *rotationGesture = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotatePiece:)];
    [faceImageView addGestureRecognizer:rotationGesture];
    [rotationGesture setDelegate:self];

    UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scalePiece:)];
    [pinchGesture setDelegate:self];
    [faceImageView addGestureRecognizer:pinchGesture];

    UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureMoveAround:)];
    [panRecognizer setMinimumNumberOfTouches:1];
    [panRecognizer setMaximumNumberOfTouches:2];
    [panRecognizer setDelegate:self];
    [faceImageView addGestureRecognizer:panRecognizer];


    [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationNone];

    [appDelegate fadeObject:moveIcons StartAlpha:0 FinishAlpha:1 Duration:2];
    currentTimer = [NSTimer timerWithTimeInterval:4.0f target:self selector:@selector(fadeoutMoveicons) userInfo:nil repeats:NO];

    [[NSRunLoop mainRunLoop] addTimer: currentTimer forMode: NSDefaultRunLoopMode];

}

Answer 1

以下代码使用计算出的比例因子创建封闭 View (faceImageView 的 super View ，其中 clipsToBounds 设置为 YES)的快照。

假设faceImageView的内容模式为UIViewContentModeScaleAspectFit，并且faceImageView的框架设置为enendingView的边界。

- (UIImage *)captureView {

    float imageScale = sqrtf(powf(faceImageView.transform.a, 2.f) + powf(faceImageView.transform.c, 2.f));    
    CGFloat widthScale = faceImageView.bounds.size.width / faceImageView.image.size.width;
    CGFloat heightScale = faceImageView.bounds.size.height / faceImageView.image.size.height;
    float contentScale = MIN(widthScale, heightScale);
    float effectiveScale = imageScale * contentScale;

    CGSize captureSize = CGSizeMake(enclosingView.bounds.size.width / effectiveScale, enclosingView.bounds.size.height / effectiveScale);

    NSLog(@"effectiveScale = %0.2f, captureSize = %@", effectiveScale, NSStringFromCGSize(captureSize));

    UIGraphicsBeginImageContextWithOptions(captureSize, YES, 0.0);        
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(context, 1/effectiveScale, 1/effectiveScale);
    [enclosingView.layer renderInContext:context];   
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return img;
}

根据当前变换，生成的图像将具有不同的大小。例如，当您放大时，尺寸会变小。您还可以将 effectScale 设置为常量值，以获得具有常量大小的图像。

您的手势识别器代码不限制比例因子，即您可以不受限制地缩小/放大。这可能非常危险!当您缩小很多时，我的捕获方法可以输出非常大的图像。

如果缩小，捕获图像的背景将为黑色。如果您希望它是透明的，则必须将UIGraphicsBeginImageContextWithOptions的opaque-参数设置为NO。