从 iOS 上的 UIView 将图像保存到应用程序文档文件夹

Posted 2023-02-24

【中文标题】从 iOS 上的 UIView 将图像保存到应用程序文档文件夹

【英文标题】：Save An Image To Application Documents Folder From UIView On IOS

【发布时间】：2011-07-25 19:51:09

【问题描述】：

我有一个 UIImageView，它允许用户放置和保存图像，直到可以保存为止。问题是，我不知道如何实际保存和检索我放置在视图中的图像。

我已经像这样检索图像并将其放置在 UIImageView 中：

//Get Image 
- (void) getPicture:(id)sender 
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    picker.delegate = self;
    picker.allowsEditing = YES;
    picker.sourceType = (sender == myPic) ? UIImagePickerControllerSourceTypeCamera : UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    [self presentModalViewController:picker animated:YES];
    [picker release];



- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage (UIImage *)image editingInfo:(NSDictionary *)editingInfo 
    myPic.image = image;
    [picker dismissModalViewControllerAnimated:YES];

它在我的 UIImageView 中显示选定的图像就好了，但我不知道如何保存它。我将视图的所有其他部分（主要是 UITextfield）保存在 Core Data 中。我已经搜索和搜索，并尝试了人们建议的许多代码，但要么我没有正确输入代码，要么这些建议不适用于我设置代码的方式。很可能是前者。我想使用我用来将文本保存在 UITextFields 中的相同操作（保存按钮）将图像保存在 UIImageView 中。以下是我保存 UITextField 信息的方式：

// Handle Save Button
- (void)save 

    // Get Info From UI
    [self.referringObject setValue:self.myInfo.text forKey:@"myInfo"];

就像我之前说的，我已经尝试了几种方法来让它工作，但无法掌握它。我有生以来第一次想对一个无生命的物体造成身体伤害，但我设法克制了自己。

我希望能够将用户放置到 UIImageView 中的图像保存在应用程序的文档文件夹中，然后能够检索它并将其放置在另一个 UIImageView 中，以便在用户将该视图推送到堆栈时显示.非常感谢任何帮助！

【参考方案1】：

一切都很好，伙计。不要伤害自己或他人。

您可能不想将这些图像存储在 Core Data 中，因为如果数据集变得太大，这会影响性能。最好将图像写入文件。

NSData *pngData = UIImagePNGRepresentation(image);

这会提取您捕获的图像的 PNG 数据。从这里，您可以将其写入文件：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
NSString *documentsPath = [paths objectAtIndex:0]; //Get the docs directory 
NSString *filePath = [documentsPath stringByAppendingPathComponent:@"image.png"]; //Add the file name
[pngData writeToFile:filePath atomically:YES]; //Write the file

稍后阅读它的工作方式相同。像我们上面那样构建路径，然后：

NSData *pngData = [NSData dataWithContentsOfFile:filePath];
UIImage *image = [UIImage imageWithData:pngData];

您可能想要做的是创建一个为您创建路径字符串的方法，因为您不希望代码到处乱扔。它可能看起来像这样：

- (NSString *)documentsPathForFileName:(NSString *)name

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);  
    NSString *documentsPath = [paths objectAtIndex:0];

    return [documentsPath stringByAppendingPathComponent:name]; 

希望对您有所帮助。

【讨论】：

完全正确 - 只是想提一下 Apple 存储指南，因此取决于图像的性质，它应该存储在缓存下

我听从了你的建议和代码。但它没有出现在照片部分。这是怎么发生的？

@DaniloCampos 如何在 Documents Directory 中创建一个文件夹，然后将文件保存在该文件夹中？

【参考方案2】：

Swift 3.0 版本

let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as NSString
        
let img = UIImage(named: "1.jpg")!// Or use whatever way to get the UIImage object
let imgPath = URL(fileURLWithPath: documentDirectoryPath.appendingPathComponent("1.jpg"))// Change extension if you want to save as PNG

do
    try UIImageJPEGRepresentation(img, 1.0)?.write(to: imgPath, options: .atomic)//Use UIImagePNGRepresentation if you want to save as PNG
catch let error
    print(error.localizedDescription)

【参考方案3】：

带有扩展的 Swift 4

extension UIImage

func saveImage(inDir:FileManager.SearchPathDirectory,name:String)
    guard let documentDirectoryPath = FileManager.default.urls(for: inDir, in: .userDomainMask).first else 
        return
    
    let img = UIImage(named: "\(name).jpg")!

    // Change extension if you want to save as PNG.
    let imgPath = URL(fileURLWithPath: documentDirectoryPath.appendingPathComponent("\(name).jpg").absoluteString)
    do 
        try UIImageJPEGRepresentation(img, 0.5)?.write(to: imgPath, options: .atomic)
     catch 
        print(error.localizedDescription)
    
  

使用示例

 image.saveImage(inDir: .documentDirectory, name: "pic")

【参考方案4】：

这是Fangming Ning's answer for Swift 4.2，更新为recommended and more Swifty method 用于检索文档目录路径和更好的文档。也感谢方明宁的新方法。

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


//Using force unwrapping here because we're sure "1.jpg" exists. Remember, this is just an example.
let img = UIImage(named: "1.jpg")!

// Change extension if you want to save as PNG.
let imgPath = documentDirectoryPath.appendingPathComponent("1.jpg")

do 
    //Use .pngData() if you want to save as PNG.
    //.atomic is just an example here, check out other writing options as well. (see the link under this example)
    //(atomic writes data to a temporary file first and sending that file to its final destination)
    try img.jpegData(compressionQuality: 1)?.write(to: imgPath, options: .atomic)
 catch 
    print(error.localizedDescription)

Check out all the possible Data writing options here.

【讨论】：

这是正确的吗？在回答另一个问题here 时，我发现fileURLWithPath 和absoluteString 是错误的。

@dumbledad 感谢您提供的信息，我已经更新了我的答案并重写了 Swift 4.2 的代码。

【参考方案5】：

#pragma mark - Save Image To Local Directory

- (void)saveImageToDocumentDirectoryWithImage:(UIImage *)capturedImage 
    NSError *error;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
    NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"/images"];
    
    //Create a folder inside Document Directory
    if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
        [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error]; //Create folder

    NSString *imageName = [NSString stringWithFormat:@"%@/img_%@.png", dataPath, [self getRandomNumber]] ;
    // save the file
    if ([[NSFileManager defaultManager] fileExistsAtPath:imageName]) 
        // delete if exist
        [[NSFileManager defaultManager] removeItemAtPath:imageName error:nil];
    
    
    NSData *imageDate = [NSData dataWithData:UIImagePNGRepresentation(capturedImage)];
    [imageDate writeToFile: imageName atomically: YES];



#pragma mark - Generate Random Number

- (NSString *)getRandomNumber 
    NSTimeInterval time = ([[NSDate date] timeIntervalSince1970]); // returned as a double
    long digits = (long)time; // this is the first 10 digits
    int decimalDigits = (int)(fmod(time, 1) * 1000); // this will get the 3 missing digits
    //long timestamp = (digits * 1000) + decimalDigits;
    NSString *timestampString = [NSString stringWithFormat:@"%ld%d",digits ,decimalDigits];
    return timestampString;

【参考方案6】：

在斯威夫特中：

let paths: [NSString?] = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .LocalDomainMask, true)
if let path = paths[0]?.stringByAppendingPathComponent(imageName) 
    do 
        try UIImagePNGRepresentation(image)?.writeToFile(path, options: .DataWritingAtomic)
     catch 
        return