如何保存调整大小的图像？

Posted 2023-03-07

【中文标题】如何保存调整大小的图像？

【英文标题】：How to save resized images?

【发布时间】：2017-05-11 23:16:37

【问题描述】：

晚上好

我正在尝试将调整大小的图像保存在文档目录中，以避免每次调用时都必须调整大小。

分析问题只是当我使用以下行时：

let jpgImageData = UIImageJPEGRepresentation (image, 1.0)

UIImageJPEGRepresentation 似乎撤消了对图像所做的更改，从而以相同的比例保存了图像。

有人知道解决这个问题的方法吗？

代码下方：

import UIKit
class ViewController: UIViewController 
    @IBOutlet weak var imgView: UIImageView!
    override func viewDidLoad() 
        super.viewDidLoad()
        let myImageName = "image_10001.jpg"
        let imagePath = fileInDocumentsDirectory(filename: myImageName)
        if let image = UIImage(named:"image_10001")?.resizedImage(newSize: UIScreen.main.bounds.size)
            print("Image : \(image.size.height)")
            _ = saveImage(image: image, path: imagePath)
        
        if let loadedImage = loadImageFromPath(path: imagePath)
            print("Screen: \(UIScreen.main.bounds.size.height)")
            print("Image Size: \(loadedImage.size.height)")
    //            let image = UIImageJPEGRepresentation(loadedImage, 0.9)
    //            let imgRes = UIImage(data: image!)?.resizedImage(newSize: UIScreen.main.bounds.size)
    ////            
    //            let load = loadedImage.resizedImage(newSize: UIScreen.main.bounds.size)
    //            
    //            print("Load: \(load.size.height)")
    //            
    //            _  = saveImage(image: load, path: imagePath)
    //            
             imgView.image =  loadedImage
    //
    //            imgView.image = UIImage(data: image!)?.resizedImage(newSize: UIScreen.main.bounds.size)
        
        // Do any additional setup after loading the view, typically from a nib.
    

    func loadImageFromPath(path: String) -> UIImage? 
        let image = UIImage(contentsOfFile: path)
        if image == nil 
            print("missing image at: \(path)")
        
        print("Loading image from path: \(path)") // this is just for you to see the path in case you want to go to the directory, using Finder.
        return image
    
    func getDocumentsURL() -> URL 
        let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
        return documentsURL
    
    func fileInDocumentsDirectory(filename: String) -> String 
        let fileURL = getDocumentsURL().appendingPathComponent(filename)
        return fileURL.path
    
    func saveImage (image: UIImage, path: String ) -> Bool
        print("Save")
        let url = URL(fileURLWithPath: path)
    //        let pngImageData = UIImagePNGRepresentation(image)
        let jpgImageData = UIImageJPEGRepresentation(image, 1.0)   // if you want to save as JPEG
        let img = UIImage(data:jpgImageData!)
     //        
          print("SIMG: \(String(describing: img?.size.height))")
        do 
            _ = try jpgImageData?.write(to: url, options: .atomicWrite)
            print("Save Success")
         catch let error 
            print(error)
            return false
        
        return true
    
    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

---

extension UIImage 
    /// Returns a image that fills in newSize
    func resizedImage(newSize: CGSize) -> UIImage 
        // Guard newSize is different
        guard self.size != newSize else  return self 
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
        self.draw(in: CGRect(x:0, y:0, width:newSize.width, height: newSize.height))
        let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return newImage
    
    /// Returns a resized image that fits in rectSize, keeping it's aspect ratio
    /// Note that the new image size is not rectSize, but within it.
    func resizedImageWithinRect(rectSize: CGSize) -> UIImage 
        let widthFactor = size.width / rectSize.width
        let heightFactor = size.height / rectSize.height
        var resizeFactor = widthFactor
        if size.height > size.width 
            resizeFactor = heightFactor
        
        let newSize = CGSize(width:size.width/resizeFactor, height:size.height/resizeFactor)
        let resized = resizedImage(newSize: newSize)
        return resized
    
    var jpeg: Data? 
        return UIImageJPEGRepresentation(self, 1)   // QUALITY min = 0 / max = 1
    
    var png: Data? 
        return UIImagePNGRepresentation(self)
    

---

extension Data 
    var uiImage: UIImage? 
        return UIImage(data: self)
    

【问题讨论】：

UIImageJpgRepresentation doubles image resolution的可能重复

【参考方案1】：

我假设您的文档目录中有一些“旧”图像，它与您拥有的一些旧代码（未调整大小）一起保存。

我假设因为您发布的代码不会保存任何新图像，因为这行：

if let image = UIImage(named:"image_10001")?.resizedImage(newSize: UIScreen.main.bounds.size)
    //resize code

我认为您想在这里使用刚刚从捆绑包中获取的相同图像名称：

if let image = UIImage(named: myImageName)?.resizedImage(newSize: UIScreen.main.bounds.size)
    //resize code

您可以重置模拟器内容并确认您在此处发布的代码不会加载任何图像。

【讨论】：

所以 Krukowski 夫人的代码工作正常，问题正是我调用 let jpgImageData = UIImageJPEGRepresentation (image, 1.0) 在此行之前，我的图像调整了比例，但是当我调用此行并设置图像时例如 let img = UIImage(data: jpg).size.height，这个图像有正常大小。其余的一切正常

对我来说一切都很好。保存显示2208.0，加载图片显示：2208.0。你的照片展示了什么？

所以我发现了问题 Mrs Krukowski 在这个主题中：***.com/questions/43704615/… UIImageJPEGRepresentation 将图像大小加倍，因为未设置比例。所以当我调整大小时我的图像出现例如 1000 当我加载图像时出现 2000 但比例是 1 而不是 2。所以无论如何我需要调整图像的大小

啊，没想到。然后你可以关闭问题