Save An Image To Application Documents Folder From UIView On IOS

It's all good, man. Don't harm yourself or others.

You probably don't want to store these images in Core Data, since that can impact performance if the data set grows too large. Better to write the images to files.

NSData *pngData = UIImagePNGRepresentation(image);

This pulls out PNG data of the image you've captured. From here, you can write it to a file:

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

Reading it later works the same way. Build the path like we just did above, then:

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

What you'll probably want to do is make a method that creates path strings for you, since you don't want that code littered everywhere. It might look like this:

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

    return [documentsPath stringByAppendingPathComponent:name]; 
}

Hope that's helpful.

Swift 3.0 version

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)
}

Swift 4 with extension

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)
    }
  }
}

Usage example

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

This is Fangming Ning's answer for Swift 4.2, updated with a recommended and more Swifty method for retrieving the document directory path and with better documentation. Credits to Fangming Ning for the new method as well.

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.