如何快速在PhotoLibrary或相机中裁剪4 * 3图像 [英] How to crop a 4*3 image in photoLibrary or camera in swift

问题描述

我想在使用相机或从photoLibrary中选择后裁剪图像。

I want to crop the image after using camera or select from photoLibrary.

目前，我只能裁剪方形图像，不知道如何裁剪一张4 * 3的图片。

For now, I can only crop the square image and I have no idea how to crop a 4*3 image.

这是我的一部分代码

let imagePicker : UIImagePickerController = UIImagePickerController()
imagePicker.delegate = self
imagePicker.sourceType = .PhotoLibrary
imagePicker.allowsEditing = true

推荐答案

我不知道不允许链接作为答案。在这里，我将尝试回答这个问题。

I did not know that links are not permitted as answer. Here I will try to answer the question.

目标：以预定比例裁剪图像。
方法：

Aim: Crop image with a predefined ratio. Approach:

• 在视图控制器中-我们需要添加滚动视图-这样我们才能
  放置图像


• 设置滚动视图高度和视图高度比例的约束（可能
  为0.8）-保留视图的20％来放置按钮


• 设置滚动视图的高度和宽度比例的约束（在此
  情况下为4：3）以编程方式添加Imageview（设置所选
  图像的高度和宽度）


• 设置滚动视图的最小和最大缩放比例，以在滚动视图中正确放置较小和
  的图像。


• 在显示图像时我们将确保imageview适合
  的高度或宽度。

• In the viewcontroller - we need to add a scrollview - so that we can put the image there and zoom or pan if required.
• Set a constrain for the scrollview height and view height ratio(may be 0.8) - left 20% of the view to put the buttons.
• set a constrain for the scrollview height and width ratio (in this case 4:3) Programmatically add Imageview (set size of the selected image's height and width )
• Set scrollview minimum and maximum zoom scale to fit smaller and larger images in the scrollview properly.
• while displaying the image we will make sure imageview either fits by height or width.

现在运行应用程序，看看是否只能查看以4：3比例的滚动视图显示图像。

Now run the application see if we can view only the image in an 4:3 ratio scrollview.

对于save选项，只需映射滚动视图的坐标并从imageview获取图像（此处需要使用缩放规模）

For the save option just map the coordinates of the scrollview and get the image from the imageview (here we need to use the zoom scale)

代码：

var imgview: UIImageView!
    var imagepicked:UIImage!
    var  minZoomScale:CGFloat!
    let picker = UIImagePickerController()
    @IBOutlet weak var scrollViewSquare: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()
        picker.delegate = self
        scrollViewSquare.delegate = self
    }
func imagePickerController(
        picker: UIImagePickerController,
        didFinishPickingMediaWithInfo info: [String : AnyObject])
    {
        imagepicked = (info[UIImagePickerControllerOriginalImage] as? UIImage)!
        ImageViewInit()
        dismissViewControllerAnimated(false, completion: nil)        
    }

    @IBAction func Pick(sender: AnyObject) {
        picker.allowsEditing = false
        picker.sourceType = .PhotoLibrary
        presentViewController(picker, animated: true, completion: nil)
    }
func ImageViewInit(){
       imgview = UIImageView()
        imgview.frame =  CGRectMake(0, 0, imagepicked.size.width, imagepicked.size.height)
        imgview.image = imagepicked
        imgview.contentMode = .ScaleAspectFit
        imgview.backgroundColor = UIColor.lightGrayColor()
        scrollViewSquare.maximumZoomScale=4;
        scrollViewSquare.minimumZoomScale=0.02;
        scrollViewSquare.bounces=true;
        scrollViewSquare.bouncesZoom=true;
        scrollViewSquare.contentMode = .ScaleAspectFit
        scrollViewSquare.contentSize = imagepicked.size
        scrollViewSquare.autoresizingMask = UIViewAutoresizing.FlexibleWidth
        scrollViewSquare.addSubview(imgview)
        setZoomScale()
    }
    //fit imageview in the scrollview
    func setZoomScale(){
        let imageViewSize = imgview.bounds.size
        let scrollViewSize = scrollViewSquare.bounds.size
        let widthScale = scrollViewSize.width / imageViewSize.width
        let heightScale = scrollViewSize.height / imageViewSize.height
        minZoomScale = max(widthScale, heightScale)
        scrollViewSquare.minimumZoomScale = minZoomScale
        scrollViewSquare.zoomScale = minZoomScale
    }

    func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        return imgview
    }
//mapping the image from the scrollview to imageview to get the desired ratio 
    @IBAction func Save(sender: AnyObject) {
            let offset = scrollViewSquare.contentOffset
            let visibleRect: CGRect = CGRectMake(offset.x, offset.y, offset.x+scrollViewSquare.frame.width, offset.y+scrollViewSquare.frame.height)
            let visibleImgRect: CGRect = CGRectMake(offset.x/scrollViewSquare.zoomScale, offset.y/scrollViewSquare.zoomScale, (offset.x+scrollViewSquare.frame.width)/scrollViewSquare.zoomScale, (offset.y+scrollViewSquare.frame.height)/scrollViewSquare.zoomScale)
            print("content offset now\(offset) and visible rect is \(visibleRect)  - zoomlevel \(scrollViewSquare.zoomScale)  now image \(imagepicked.size) and current visible area in image is \(visibleImgRect)")
        }

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