如何在保留原始图像纵横比的同时将 uiimageview 内的 uiimage 向右移动？答案

【问题标题】：How do you move the uiimage inside the uiimageview to the right while retaining the aspect ratio of the original image?如何在保留原始图像纵横比的同时将 uiimageview 内的 uiimage 向右移动？
【发布时间】：2020-12-11 02:33:05
【问题描述】：

当用户使用 uiimagepicker 导入图像时，我想将图像向右移动，但是当我设置内容模式 = .right 时，会发生这种情况：The image enlarges for some reason and it looks like it moves to the left

有什么办法可以保持uiimageview的纵横比和导入图片的纵横比，同时在image view里面也向右移动。

This is how I want it to be

【问题讨论】：

UIImageView 没有“aspectFIt 和对齐”功能。不过，您可以通过多种方式完成此操作...一种是使用带有图像视图的子类视图作为子视图...搜索uiimageview aspect fit align 以获得大量结果。这个可能对你有用：github.com/sochalewski/UIImageViewAlignedSwift

标签： swift uiimageview uiimagepickercontroller

【解决方案1】：

将您的 UIImage 内容模式设置为方面填充或方面适合。然后使用自动布局。

【讨论】：

【解决方案2】：

这是一种方法：自定义视图，使用将内容设置为图像的子图层...

添加CALayer 作为子层
计算视图边界内图像的纵横比缩放矩形
将图像层的框架设置为缩放的矩形
然后根据所需的对齐方式设置图层的原点

一个简单的例子：

class AspectAlignImageView: UIView {
    
    enum AspectAlign {
        case top, left, right, bottom, center
    }
    
    // this is an array so we can set two options
    //  if, for example, we don't know if the image will be
    //  taller or narrower
    //  for example:
    //      [.top, .right] will put a
    //          wide image aligned top
    //          narrow image aligned right
    public var alignment: [AspectAlign] = [.center]
    public var image: UIImage?
    
    private let imgLayer: CALayer = CALayer()
    
    override func layoutSubviews() {
        super.layoutSubviews()
        
        // make sure we have an image
        if let img = image {
            // only add the sublayer once
            if imgLayer.superlayer == nil {
                layer.addSublayer(imgLayer)
            }
            imgLayer.contentsGravity = .resize
            imgLayer.contents = img.cgImage

            // calculate the aspect-scaled rect inside our bounds
            var scaledImageRect = CGRect.zero
            let aspectWidth:CGFloat = bounds.width / img.size.width
            let aspectHeight:CGFloat = bounds.height / img.size.height
            let aspectRatio:CGFloat = min(aspectWidth, aspectHeight)
            scaledImageRect.size.width = img.size.width * aspectRatio
            scaledImageRect.size.height = img.size.height * aspectRatio

            // set image layer frame to aspect-scaled rect
            imgLayer.frame = scaledImageRect
            
            // align as specified
            if alignment.contains(.top) {
                imgLayer.frame.origin.y = 0
            }
            if alignment.contains(.left) {
                imgLayer.frame.origin.x = 0
            }
            if alignment.contains(.bottom) {
                imgLayer.frame.origin.y = bounds.maxY - scaledImageRect.height
            }
            if alignment.contains(.right) {
                imgLayer.frame.origin.x = bounds.maxX - scaledImageRect.width
            }
        }
    }
    
}

class TestAlignViewController: UIViewController {

    let testView = AspectAlignImageView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        testView.translatesAutoresizingMaskIntoConstraints = false
        
        view.addSubview(testView)
        
        NSLayoutConstraint.activate([
            // constrain test view 240x240 square
            testView.widthAnchor.constraint(equalToConstant: 240.0),
            testView.heightAnchor.constraint(equalTo: testView.widthAnchor),
            // centered in view
            testView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            testView.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        ])
        
        if let img = UIImage(named: "bottle") {
            testView.image = img
        }
        testView.alignment = [.right]
    
        // so we can see the actual view frame
        testView.backgroundColor = .green
    }
    
}

使用这张图片：

在 240x240 视图中（视图背景设置为绿色，以便我们可以看到它的框架），我们得到以下结果：

【讨论】：