保存图像然后在 Swift (iOS) 中加载它

Question

我正在使用 saveImage 保存图像。

func saveImage (image: UIImage, path: String ) -> Bool{

    let pngImageData = UIImagePNGRepresentation(image)
    //let jpgImageData = UIImageJPEGRepresentation(image, 1.0)   // if you want to save as JPEG

    print("!!!saving image at:  \(path)")

    let result = pngImageData!.writeToFile(path, atomically: true)

    return result
}

新信息：

保存文件不能正常工作（打印“[-] ERROR SAVING FILE”）--

            // save your image here into Document Directory
        let res = saveImage(tempImage, path: fileInDocumentsDirectory("abc.png"))
        if(res == true){
            print ("[+] FILE SAVED")
        }else{
            print ("[-] ERROR SAVING FILE")
        }

为什么 saveImage 函数不保存图像？访问权？

旧信息：

调试信息说：

!!!saving image at:  file:///var/mobile/Applications/BDB992FB-E378-4719-B7B7-E9A364EEE54B/Documents/tempImage

然后我使用检索此位置

fileInDocumentsDirectory("tempImage")

结果是正确的。

然后我使用这个路径加载文件

    let image = UIImage(contentsOfFile: path)

    if image == nil {

        print("missing image at: \(path)")
    }else{
        print("!!!IMAGE FOUND at: \(path)")
    }

路径是正确的，但消息是“缺少图像...”。该文件是否以某种方式无法访问或未存储？这种行为的原因可能是什么？

我正在使用 ios 7 的 iphone 4 和带有 ios 7 模拟器的 iphone 5 上测试此代码。

编辑： 1.fileInDocumentsDirectory函数

func fileInDocumentsDirectory(filename: String) -> String {

    let documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
    let fileURL = documentsURL.URLByAppendingPathComponent(filename).absoluteString
    return fileURL        
}

Answer 1

Ashish 的评论为答案提供了线索。如果您阅读 UIImage(contentsOfFile:) 上的文档，他们会说

path 文件的路径。此路径应包含文件名 标识图像数据类型的扩展。

imageNamed 调用足够聪明，可以尝试使用 .png 和 .jpg 扩展名，但 contentsOfFile 调用需要包含扩展名的完整路径。

Answer 2

您应该使用扩展名保存图像名称，以便您的路径应该像，

///var/mobile/Applications/BDB992FB-E378-4719-B7B7-E9A364EEE54B/Documents/tempImage.png

第二件事替换下面的行，

   let result = pngImageData!.writeToFile(path, atomically: true)

与

    let result = pngImageData!.writeToFile(path, atomically: false)

atomically的参数需要设置为false。

原子地：

如果为真，则将数据写入备份文件，然后——假设没有发生错误——备份文件被重命名为路径指定的名称；否则，数据直接写入路径。

希望这会有所帮助:)

Answer 3

您必须在 Documents 目录中创建一个目录才能存储文件。

Answer 4

如果你想从服务器加载图像，你可以这样做

 let url = URL(string: "http://live-wallpaper.net/iphone/img/app/i/p/iphone-4s-wallpapers-mobile-backgrounds-dark_2466f886de3472ef1fa968033f1da3e1_raw_1087fae1932cec8837695934b7eb1250_raw.jpg")
        URLSession.shared.dataTask(with: url!) { (data, response, error) in
            guard
                let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
                let mimeType = response?.mimeType, mimeType.hasPrefix("image"),
                let data = data, error == nil
                else { return }
                DispatchQueue.main.async() { () -> Void in
                let fileManager = FileManager.default
                let paths = (NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString).appendingPathComponent("apple.jpg")
                print(paths)
                fileManager.createFile(atPath: paths as String, contents: data, attributes: nil)

            }}.resume()

Answer 5

此功能将在文档文件夹中保存图像：

func saveImage(image: UIImage) -> Bool {
    guard let data = UIImageJPEGRepresentation(image, 1) ?? UIImagePNGRepresentation(image) else {
        return false
    }
    guard let directory = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false) as NSURL else {
        return false
    }
    do {
        try data.write(to: directory.appendingPathComponent("fileName.png")!)
        return true
    } catch {   
        print(error.localizedDescription)
        return false
    }
}

使用方法：

let success = saveImage(image: UIImage(named: "image.png")!)

---

此函数将获取该图像：

func getSavedImage(named: String) -> UIImage? {
    if let dir = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false) {
        return UIImage(contentsOfFile: URL(fileURLWithPath: dir.absoluteString).appendingPathComponent(named).path)
    }
    return nil
}

使用方法：

if let image = getSavedImage(named: "fileName") {
    // do something with image
}

Answer 6

iOS 13+ Swift 5.1

iOS 12 引入了一些 API 更改。

func saveImage(imageName: String, image: UIImage) {


 guard let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return }

    let fileName = imageName
    let fileURL = documentsDirectory.appendingPathComponent(fileName)
    guard let data = image.jpegData(compressionQuality: 1) else { return }

    //Checks if file exists, removes it if so.
    if FileManager.default.fileExists(atPath: fileURL.path) {
        do {
            try FileManager.default.removeItem(atPath: fileURL.path)
            print("Removed old image") 
        } catch let removeError {
            print("couldn't remove file at path", removeError)
        }

    }

    do {
        try data.write(to: fileURL)
    } catch let error {
        print("error saving file with error", error) 
    }

}



func loadImageFromDiskWith(fileName: String) -> UIImage? {

  let documentDirectory = FileManager.SearchPathDirectory.documentDirectory

    let userDomainMask = FileManager.SearchPathDomainMask.userDomainMask
    let paths = NSSearchPathForDirectoriesInDomains(documentDirectory, userDomainMask, true)

    if let dirPath = paths.first {
        let imageUrl = URL(fileURLWithPath: dirPath).appendingPathComponent(fileName)
        let image = UIImage(contentsOfFile: imageUrl.path)
        return image

    }

    return nil
}

Answer 7

详情

• Xcode 版本 10.2 (10E125)，Swift 5

解决方案

// save
extension UIImage {

    func save(at directory: FileManager.SearchPathDirectory,
              pathAndImageName: String,
              createSubdirectoriesIfNeed: Bool = true,
              compressionQuality: CGFloat = 1.0)  -> URL? {
        do {
        let documentsDirectory = try FileManager.default.url(for: directory, in: .userDomainMask,
                                                             appropriateFor: nil,
                                                             create: false)
        return save(at: documentsDirectory.appendingPathComponent(pathAndImageName),
                    createSubdirectoriesIfNeed: createSubdirectoriesIfNeed,
                    compressionQuality: compressionQuality)
        } catch {
            print("-- Error: \(error)")
            return nil
        }
    }

    func save(at url: URL,
              createSubdirectoriesIfNeed: Bool = true,
              compressionQuality: CGFloat = 1.0)  -> URL? {
        do {
            if createSubdirectoriesIfNeed {
                try FileManager.default.createDirectory(at: url.deletingLastPathComponent(),
                                                        withIntermediateDirectories: true,
                                                        attributes: nil)
            }
            guard let data = jpegData(compressionQuality: compressionQuality) else { return nil }
            try data.write(to: url)
            return url
        } catch {
            print("-- Error: \(error)")
            return nil
        }
    }
}

// load from path

extension UIImage {
    convenience init?(fileURLWithPath url: URL, scale: CGFloat = 1.0) {
        do {
            let data = try Data(contentsOf: url)
            self.init(data: data, scale: scale)
        } catch {
            print("-- Error: \(error)")
            return nil
        }
    }
}

用法

// save image (way 1)
let path = "photo/temp/album1/img.jpg"
guard   let img = UIImage(named: "img"),
        let url = img.save(at: .documentDirectory,
                           pathAndImageName: path) else { return }
print(url)

// get image from directory
guard let img2 = UIImage(fileURLWithPath: url) else { return }

// save image (way 2)
let tempDirectoryUrl = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(path)
guard let url2 = img2.save(at: tempDirectoryUrl) else { return }
print(url2)

检查结果

open the iOS simulator directory

Answer 8

斯威夫特 5

func saveImage(image: UIImage) -> Bool{
    guard let data = image.jpegData(compressionQuality: 1) ?? image.pngData() else {
        return false
    }
    guard let directory = try? FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false) as NSURL else {
        return false
    }
    do{
        try data.write(to: directory.appendingPathComponent("\(txtNom.text!).png")!)
        print(directory)
        print(data)
        print("si se pudo")
        return true
    } catch {
        print(error.localizedDescription)
        return false
    }
} // saveImage

Answer 9

我前段时间在 StackOverFlow 上找到了解决方案。作者不记得了

假设 yourImage 是 UIImage()

let ciImage = yourImage!.ciImage
let context = CIContext()
let cgImage = context.createCGImage(ciImage!, from: ciImage!.extent)
let uiImage = UIImage(cgImage: cgImage!)

UIImageWriteToSavedPhotosAlbum(uiImage, self, 
#selector(self.image(_:didFinishSavingWithError:contextInfo:)), nil)

还有这个功能

@objc func image(_ image: UIImage, didFinishSavingWithError error: Error?, contextInfo: UnsafeRawPointer) {
if let error = error {
    // we got back an error!
    let ac = UIAlertController(title: "Save error", message: error.localizedDescription, preferredStyle: .alert)
    ac.addAction(UIAlertAction(title: "OK", style: .default))
    present(ac, animated: true)
} else {
    let ac = UIAlertController(title: "Saved!", message: "Your altered image has been saved to your photos.", preferredStyle: .alert)
    ac.addAction(UIAlertAction(title: "OK", style: .default))
    present(ac, animated: true)
}

}

Answer 10

您实际上可以使用 PHPhotoLibrary 来执行此操作。 这是保存图片和获取图片url的代码。

extension UIImage {
func saveToPhotoLibrary(completion: @escaping (URL?) -> Void) {
    var localeId: String?
    PHPhotoLibrary.shared().performChanges({
        let request = PHAssetChangeRequest.creationRequestForAsset(from: self)
        localeId = request.placeholderForCreatedAsset?.localIdentifier
    }) { (isSaved, error) in
        guard isSaved else {
            debugPrint(error?.localizedDescription)
            completion(nil)
            return
        }
        guard let localeId = localeId else {
            completion(nil)
            return
        }
        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        let result = PHAsset.fetchAssets(withLocalIdentifiers: [localeId], options: fetchOptions)
        guard let asset = result.firstObject else {
            completion(nil)
            return
        }
        getPHAssetURL(of: asset) { (phAssetUrl) in
            completion(phAssetUrl)
        }
    }
}

static func getPHAssetURL(of asset: PHAsset, completionHandler : @escaping ((_ responseURL : URL?) -> Void))
    {
            let options: PHContentEditingInputRequestOptions = PHContentEditingInputRequestOptions()
            options.canHandleAdjustmentData = {(adjustmeta: PHAdjustmentData) -> Bool in
                return true
            }
            asset.requestContentEditingInput(with: options, completionHandler: { (contentEditingInput, info) in
                completionHandler(contentEditingInput!.fullSizeImageURL)
            })

    }
}

Answer 11

将图像保存在本地 Xcode 文档目录中

传入你的图片和你想给它起的名字（你选择你想要的文件名）。

func saveImageLocally(image: UIImage, fileName: String) {
    
 // Obtaining the Location of the Documents Directory
    let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    
    // Creating a URL to the name of your file
    let url = documentsDirectory.appendingPathComponent(fileName)
    
    if let data = image.pngData() {
        do {
            try data.write(to: url) // Writing an Image in the Documents Directory
        } catch {
            print("Unable to Write \(fileName) Image Data to Disk")
        }
    }
}

阅读

使用与保存时相同的文件名

func getImageFromName(fileName: String) {
    let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let url = documentsDirectory.appendingPathComponent(fileName)
    
    if let imageData = try? Data(contentsOf: url) {
        let image = UIImage(data: imageData) // HERE IS YOUR IMAGE! Do what you want with it!
        
    } else {
        print("Couldn't get image for \(fileName)")
    }
}