ios 如何将 UIImage 保存到文件？

How do I save a UIImage to a file?

提问by user1542660

If I have a UIImagefrom an imagePicker, how can I save it to a subfolder in the documents directory?

如果我有一个UIImage来自 imagePicker 的文件，我如何将它保存到文档目录中的子文件夹中？

回答by DrummerB

Of course you can create subfolders in the documents folder of your app. You use NSFileManagerto do that.

当然，您可以在应用程序的文档文件夹中创建子文件夹。你习惯NSFileManager这样做。

You use UIImagePNGRepresentationto convert your image to NSData and save that to disk.

您用于UIImagePNGRepresentation将图像转换为 NSData 并将其保存到磁盘。

// Create path.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Image.png"];

// Save image.
[UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];

Core Data has nothing to do with saving images to disk by the way.

顺便说一下，Core Data 与将图像保存到磁盘无关。

回答by NatashaTheRobot

In Swift 3:

在 Swift 3 中：

// Create path.
let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
let filePath = "\(paths[0])/MyImageName.png"

// Save image.
UIImagePNGRepresentation(image)?.writeToFile(filePath, atomically: true)

回答by dasblinkenlight

You have to construct a representation of your image as a particular format(say, JPEG or PNG), and then call writeToFile:atomically:on the representation:

您必须将图像表示为特定格式（例如 JPEG 或 PNG），然后调用writeToFile:atomically:该表示：

UIImage *image = ...;
NSString  *path = ...;
[UIImageJPEGRepresentation(image, 1.0) writeToFile:path atomically:YES];

回答by Alex the Ukrainian

The above are useful, but they don't answer your question of how to save in a subdirectory or get the image from a UIImagePicker.

以上内容很有用，但它们没有回答您如何保存在子目录中或从 UIImagePicker 获取图像的问题。

First, you must specify that your controller implements image picker's delegate, in either .m or .h code file, such as:

首先，您必须在 .m 或 .h 代码文件中指定您的控制器实现图像选择器的委托，例如：

@interface CameraViewController () <UIImagePickerControllerDelegate>

@end

Then you implement the delegate's imagePickerController:didFinishPickingMediaWithInfo: method, which is where you can get the photograph from the image picker and save it (of course, you may have another class/object that handles the saving, but I'll just show the code inside the method):

然后你实现委托的 imagePickerController:didFinishPickingMediaWithInfo: 方法，在这里你可以从图像选择器中获取照片并保存它（当然，你可能有另一个处理保存的类/对象，但我只会展示代码方法内）：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    // get the captured image
    UIImage *image = (UIImage *)info[UIImagePickerControllerOriginalImage];


    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *imageSubdirectory = [documentsDirectory stringByAppendingPathComponent:@"MySubfolderName"];

    NSString *filePath = [imageSubdirectory stringByAppendingPathComponent:@"MyImageName.png"];

    // Convert UIImage object into NSData (a wrapper for a stream of bytes) formatted according to PNG spec
    NSData *imageData = UIImagePNGRepresentation(image); 
    [imageData writeToFile:filePath atomically:YES];
}

If you want to save as JPEG image, the last 3 lines would be:

如果要另存为 JPEG 图像，最后 3 行将是：

NSString *filePath = [imageSubdirectory stringByAppendingPathComponent:@"MyImageName.jpg"];

// Convert UIImage object into NSData (a wrapper for a stream of bytes) formatted according to JPG spec
NSData *imageData = UIImageJPEGRepresentation(image, 0.85f); // quality level 85%
[imageData writeToFile:filePath atomically:YES];

回答by neoneye

extension UIImage {
    /// Save PNG in the Documents directory
    func save(_ name: String) {
        let path: String = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
        let url = URL(fileURLWithPath: path).appendingPathComponent(name)
        try! UIImagePNGRepresentation(self)?.write(to: url)
        print("saved image at \(url)")
    }
}

// Usage: Saves file in the Documents directory
image.save("climate_model_2017.png")

回答by Maggie

NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:path atomically:YES];

where path is the name of the file you want to write it to.

其中 path 是您要将其写入的文件的名称。

回答by lu yuan

First you should get the Documents directory

首先你应该得到 Documents 目录

/* create path to cache directory inside the application's Documents directory */
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"fileName"];

Then you should save the photo to the file

然后你应该将照片保存到文件中

NSData *photoData = UIImageJPEGRepresentation(photoImage, 1);
[photoData writeToFile:filePath atomically:YES];

回答by Torianin

In Swift 4.2:

在 Swift 4.2 中：

// Create path.
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
if let filePath = paths.first?.appendingPathComponent("MyImageName.png") {
    // Save image.
    do {
       try image.pngData()?.write(to: filePath, options: .atomic)
    } catch {
       // Handle the error
    }
}

回答by Samo

In Swift 4:

在 Swift 4 中：

// Create path.
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
if let filePath = paths.first?.appendingPathComponent("MyImageName.png") {
    // Save image.
    do {
       try UIImagePNGRepresentation(image)?.write(to: filePath, options: .atomic)
    }
    catch {
       // Handle the error
    }
}