iPhone - UIImagePickerController -> save the image

问题:

I have an iPhone application using a UIImagePickerController. As sourceType I have

• UIImagePickerControllerSourceTypePhotoLibrary
• UIImagePickerControllerSourceTypeCamera
• UIImagePickerControllerSourceTypeSavedPhotosAlbum

so the user can make a photo or select one from the photo library from the photos or camera photos.

The image will be displayed in a UIImageView. The image should be saved if the user closes the app. So for text fields, I use NSUserDefaults. I know, it is not a good way to save the image inside the NSUSerDefaults with NSData, so I want to save / copy the image to a folder which is controlled by my application similar to the NSUserDefaults.

How can I do this? I want to save it, and then I can write the path to the file into my NSUserDefaults and read it on startup of the application.

Thank you in advance & Best Regards.

回答1:

You can use the following code in UIImagePickerControllerDelegate delegate implementation

- (void) imagePickerController:(UIImagePickerController *)picker
 didFinishPickingMediaWithInfo:(NSDictionary *)info {

    //obtaining saving path
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *imagePath = [documentsDirectory stringByAppendingPathComponent:@"latest_photo.png"];

    //extracting image from the picker and saving it
    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];   
    if ([mediaType isEqualToString:@"public.image"]){
        UIImage *editedImage = [info objectForKey:UIImagePickerControllerEditedImage];
        NSData *webData = UIImagePNGRepresentation(editedImage);
        [webData writeToFile:imagePath atomically:YES];
    }
}

That's all

回答2:

Depending on the file format you want to save, you can use

[UIImagePNGRepresentation(image) writeToFile:path atomically:YES];

OR

[UIImageJPEGRepresentation(image) writeToFile:path atomically:YES];

回答3:

This is the code to save the UIImage into the document directory. You can use this code in didFinishPickingImage delegate method:

// Create paths to output images
NSString  *pngPath = [NSHomeDirectory();
stringByAppendingPathComponent:@"Documents/Test.png"];
NSString  *jpgPath = [NSHomeDirectory();
stringByAppendingPathComponent:@"Documents/Test.jpg"];

// Write a UIImage to JPEG with minimum compression (best quality)
// The value 'image' must be a UIImage object
// The value '1.0' represents image compression quality as value from 0.0 to 1.0
[UIImageJPEGRepresentation(image, 1.0) writeToFile:jpgPath atomically:YES];

// Write image to PNG
[UIImagePNGRepresentation(image) writeToFile:pngPath atomically:YES];

// Let's check to see if files were successfully written...

// Create file manager
NSError *error;
NSFileManager *fileMgr = [NSFileManager defaultManager];

// Point to Document directory
NSString *documentsDirectory = [NSHomeDirectory();
stringByAppendingPathComponent:@"Documents"];

// Write out the contents of home directory to console
NSLog(@"Documents directory: %@", [fileMgr contentsOfDirectoryAtPath:documentsDirectory error:&error]);

EDIT

You can also use:

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

to find the path to your application document directory, instead of NSHomeDierctory.

回答4:

Update knuku's answer for Swift 3.0

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {

    //obtaining saving path
    let fileManager = FileManager.default
    let documentsPath = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first
    let imagePath = documentsPath?.appendingPathComponent("image.jpg")

    // extract image from the picker and save it
    if let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
        try! UIImageJPEGRepresentation(pickedImage, 0.0)?.write(to: imagePath!)
    }
    self.dismiss(animated: true, completion: nil)        
}

here the image is saved as jpeg but you can also save it as png. the 0.0 parameter stands for compression and it's the lowest quality, if you want to get the best use 1.0.