如何从UIImageView的全分辨率获得旋转，缩放和平移的图像？ [英] How to get a rotated, zoomed and panned image from an UIImageView at its full resolution?

问题描述

我有一个UIImageView可以旋转，平移和缩放与手势识别器。因此，在其封闭视图中裁剪。
一切正常，但我不知道如何以全分辨率保存图片的可见部分。这不是一个屏幕抓住。

I have an UIImageView which can be rotated, panned and scaled with gesture recognisers. As a result it is cropped in its enclosing view. Everything is working fine but I don't know how to save the visible part of the picture in its full resolution. It's not a screen grab.

我知道我从UIImageView的可见内容直接得到UIImage，但它被限制在屏幕的分辨率。

I know I get the UIImage straight from the visible content of the UIImageView but it is limited to the resolution of the screen.

我假设我必须对UIImage执行相同的转换并裁剪它。有没有一个简单的方法来做到这一点？

I assume that I have to do the same transformations on the UIImage and crop it. IS there an easy way to do that?

更新：
例如，我有一个UIImageView高分辨率的图像，假设一个8MP iPhone 4s相机照片，其被手势转换，因此它在其包围视图中被缩放，旋转和移动。显然有一些裁剪，所以只有一部分的图像显示。显示屏幕分辨率和下划线图像分辨率之间存在巨大差异，我需要一个图像的图像分辨率。 UIImageView位于 UIViewContentModeScaleAspectFit 中，但具有UIViewContentModeScaleAspectFill的解决方案也很好。

Update: For example, I have an UIImageView with an image in high resolution, let's say a 8MP iPhone 4s camera photo, which is transformed with gestures, so it becomes scaled, rotated and moved around in its enclosing view. Obviously there is some cropping going on so only a part of the image is displayed. There is a huge difference between the displayed screen resolution and the underlining image resolution, I need an image in the image resolution. The UIImageView is in UIViewContentModeScaleAspectFit, but a solution with UIViewContentModeScaleAspectFill is also fine.

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];

}

推荐答案

代码创建封装视图的快照（ faceImageView的超级视图与 clipsToBounds 设置为 YES ）使用计算的比例因子。

The following code creates a snapshot of the enclosing view (superview of faceImageView with clipsToBounds set to YES) using a calculated scale factor.

它假设faceImageView的内容模式是 UIViewContentModeScaleAspectFit 并且faceImageView的框架设置为surroundingView的边界。

It assumes that the content mode of faceImageView is UIViewContentModeScaleAspectFit and that the frame of faceImageView is set to the enclosingView's bounds.

- (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，生成的图像将有不同的大小。例如，当您放大时，尺寸变小。您还可以将 effectiveScale 设置为常量值，以获得具有常量大小的图片。

Depending on the current transform the resulting image will have a different size. For example when you zoom in, the size gets smaller. You can also set effectiveScale to a constant value in order to get an image with a constant size.

识别器代码不限制比例因子，即，您可以缩小/ in而不受限制。这可能是非常危险的！

Your gesture recognizer code does not limit the scale factor, i.e. you can zoom out/in without being limited. That can be very dangerous! My capture method can output really large images when you've zoomed out very much.

如果您已经缩小，捕获图像的背景将是黑色的。如果您希望它是透明的，您必须将 UIGraphicsBeginImageContextWithOptions 的opaque-parameter设置为 NO 。

If you have zoomed out the background of the captured image will be black. If you want it to be transparent, you must set the opaque-parameter of UIGraphicsBeginImageContextWithOptions to NO.

这篇关于如何从UIImageView的全分辨率获得旋转，缩放和平移的图像？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！