Swift 3-UIImageView图像缩小

Question

这是准备好序列的代码，然后从该序列中解散出来的代码。

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if segue.identifier == "toTossImageVC" {
        let dvc = segue.destination as! TossImageViewController
        dvc.displayedImage = tossPhoto2.image
    }
}

@IBAction func unwindToTossVC(unwindSegue: UIStoryboardSegue) {

    let dvc = unwindSegue.source as! TossImageViewController
    self.tossPhoto2.image = dvc.displayedImage
}

可以看出，在准备过程中将图像传递到目标VC，然后以展开方法检索该图像的更新版本（用户可以在目标VC中标记该图像）。

self.tossPhoto2是一个UIImage对象，并且它的contentMode在Interface Builder中设置为scaleToFill。 我的问题是，当我展开并分配tossPhoto2的图像到dvc.displayedImage时，它会严重缩水。 在对图像进行标记和标记之前：

在PhotoFine之前

然后，当我们用标签标记照片后返回该VC时，这是紧缩后的照片：

AfterPhotoShrunk

在搜索了StackOverflow和其他地方几个小时之后，解决该问题的最佳建议是将contentMode设置为.scaleAspectFit，但这没有用（并且无论如何我都希望将其保留为scaleToFill，无论如何在Interface Builder中定义）。

有什么想法为什么会发生以及如何解决这个问题？ 这是TossImageViewController中的代码（如果有帮助的话），但是我看不到如何无意间缩小图像。 这可以允许用户将标签（实现为UILabels）添加到图像上。

class TossImageViewController: UIViewController, UINavigationControllerDelegate, UIGestureRecognizerDelegate {
@IBOutlet var tossImage: UIImageView!
var displayedImage: UIImage!
let ac = UIAlertController(title: "Select Toss Type", message: nil, preferredStyle: .actionSheet)
var selectedTossType = String()
var touchPoint: CGPoint!


override func viewDidLoad() {
    super.viewDidLoad()
    tossImage.image = displayedImage

    self.tabBarController?.tabBar.isHidden = true

    let gestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(handleTap))
    self.view.addGestureRecognizer(gestureRecognizer)

    // Set up the action sheet picker
    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
    ac.addAction(cancelAction)
    let trashAction = UIAlertAction(title: "Trash", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Trash"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 80)
        print("Trash tag")
    })
    ac.addAction(trashAction)
    let sinkAction = UIAlertAction(title: "Sink Disposal", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Sink Disposal"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 120)
    })
    ac.addAction(sinkAction)
    let saveAction = UIAlertAction(title: "Save for Later", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Save for Later"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 140)
    })
    ac.addAction(saveAction)
    let animalAction = UIAlertAction(title: "Animal", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Animal"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 80)
    })
    ac.addAction(animalAction)
    let sharingAction = UIAlertAction(title: "Sharing", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Sharing"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 80)
    })
    ac.addAction(sharingAction)
    let compostAction = UIAlertAction(title: "Compost", style: .destructive, handler: {(action) -> Void in
        self.selectedTossType = "Compost"
        // Write the selected toss type where the tap happened
        self.displayedImage = self.textToImage(drawText: self.selectedTossType as NSString, inImage: self.displayedImage, atPoint: self.touchPoint, labelWidth: 80)
    })
    ac.addAction(compostAction)

}

override func viewWillDisappear(_ animated: Bool) {
    self.tabBarController?.tabBar.isHidden = false
}

@IBAction func cancel(_ sender: Any) {
    navigationController!.popViewController(animated: true)
}

func textToImage(drawText text: NSString, inImage image: UIImage, atPoint point: CGPoint, labelWidth: CGFloat) -> UIImage {

    let label = UILabel(frame: CGRect(x: (point.x - labelWidth/2), y: point.y, width: labelWidth, height: 20))
    label.textColor = .red
    label.shadowColor = .yellow
    label.text = text as String
    label.textAlignment = .center
    self.view.addSubview(label)

    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(image.size, false, scale)
    view.layer.render(in: UIGraphicsGetCurrentContext()!)
    let taggedImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return taggedImage!
}

Answer 1

好的-看来这是问题所在...

您的TossImageViewController有一个UIImageView我不知道它的大小，但可以说它是300x300。 您设置其.image = displayedImage 。 到目前为止，一切都很好...您会看到图像缩放到适合屏幕大小的大小。

接下来，在用户交互之后，您调用textToImage(...)而我猜您正在尝试将文本绘制到原始图像上吗？ 如果是这样，那不是正在发生的事情。

相反，您将UILabel添加到self.view ，创建3000 x 2002的Graphics Context，然后返回UIGraphicsGetImageFromCurrentImageContext() ...但是该图像是当前视图-可能是750 x 1334 ，位于上方，上下文的左上角。

您需要做的是：

a）创建一个3000 x 2002 UIView，在UIImageView中将图像添加为该视图的子视图，然后将UILabel（相对于大图像调整大小）添加为另一个子视图。 然后从该上下文中获取图像。 要么...

b）使用上下文和图像drawInRect和字符串drawInRect函数。

这篇文章有一些讨论和解决方案（Obj-C和Swift）： 如何在Objective-C（iOS）中的图像上编写文本？