UIScrollView 中的 CALayer 大小错误

Question

I'm trying to zoom UIImageView and UIView , which are inside the UIScrollView , but it doesn't work.

I have an UIImage and CALayer , both of them have an equal size ( 2048×2155 ). These components wrapped into UIImageView (image view) and UIView (canvas) and displayed inside UIScrollView.

The image view and canvas have the same content scale factor , which equals 2.0 (UIScreen.main.scale), but the canvas has the wrong size (see picture below).

CALayer sublayers were built by using CAShapeLayer and UIBezierPath .

The UIScrollViewDelegate looks next:

func viewForZooming(in scrollView: UIScrollView) -> UIView? {
    canvas
}

func scrollViewDidZoom(_ scrollView: UIScrollView) {
    self.scrollView.centerContentView()
}

The center content view looks next (method inside custom UIScrollView):

func centerContentView() {        
    let boundsSize = bounds.size
    var centerFrame = canvas.frame
    
    if centerFrame.size.width < boundsSize.width {
        centerFrame.origin.x = (boundsSize.width - centerFrame.size.width) / 2.0
    } else {
        centerFrame.origin.x = 0
    }
    
    if centerFrame.size.height < boundsSize.height {
        centerFrame.origin.y = (boundsSize.height - centerFrame.size.height) / 2.0
    } else {
        centerFrame.origin.y = 0
    }
    
    imageView.frame = centerFrame
    canvas.frame = centerFrame
}

All my efforts have failed. I tried to transform the CALayer with canvas but to no avail. I will be grateful for any suggestions or help. Thank you.

Answer 1

The problem was fixed by using the next lines:

let scale = UIScreen.main.bounds.width / imageSize.height
let scaleTransformation = CATransform3DMakeScale(scale, scale, 1)

for layer in layers { 
   layer.transform = scaleTransformation
}

where the imageSize equals to the 2048×2155 and everything works fine. Thank you.