Saving an image displayed in a UIImageView - ios

Question

I have an array of images that are displayed in a UICollectionView.
When a cell in the collection view is pressed, that image is pushed to a view controller and displayed in a UIImageView.
I want to then be able to press a button and save the image to the users camera roll.
But I'm having some trouble doing so...
I think I'm on the right lines with the code but can't get it all to work together:
- (IBAction)onClickSavePhoto:(id)sender{
UIImage *img = [UIImage imageNamed:#"which ever image is being currently displayed in the image view"];
UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);
}
How can i manipulate the code to allow the user to save the image displayed in the image view?
Thanks in advance!
UPDATE:
Found the solution to the problem in another post:
Save image in UIImageView to iPad Photos Library

Answer 1

How to save an image to the library:
You can use this function:
UIImageWriteToSavedPhotosAlbum(UIImage *image,
id completionTarget,
SEL completionSelector,
void *contextInfo);
You only need completionTarget, completionSelector and contextInfo if you want to be notified when the UIImage is done saving, otherwise you can pass in nil.
More info here
Supposedly a faster way to save an image to the library than using UIImageWriteToSavedPhotosAlbum:
There`s much more fast then UIImageWriteToSavedPhotosAlbum way to do it using iOS 4.0+ AVFoundation framework
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library writeImageToSavedPhotosAlbum:[image CGImage] orientation:(ALAssetOrientation)[image imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error){
if (error) { // TODO: error handling }
else { // TODO: success handling }
}];
//for non-arc projects
//[library release];
Get image of whatever is in the UIImageView as a screenshot:
iOS 7 has a new method that allows you to draw a view hierarchy into the current graphics context. This can be used to get an UIImage very fast.
This is a category method on UIView to get the view as an UIImage:
- (UIImage *)takeSnapShot {
UIGraphicsBeginImageContextWithOptions(self.myImageView.bounds.size, NO, [UIScreen mainScreen].scale);
[self drawViewHierarchyInRect:self.myImageView.bounds afterScreenUpdates:YES];
// old style [self.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
It is considerably faster then the existing renderInContext: method.
Reference : https://developer.apple.com/library/ios/qa/qa1817/_index.html
UPDATE FOR SWIFT: An extension that does the same:
extension UIView {
func takeSnapshot() -> UIImage {
UIGraphicsBeginImageContextWithOptions(self.myImageView.bounds.size, false, UIScreen.mainScreen().scale);
self.drawViewHierarchyInRect(self.myImageView.bounds, afterScreenUpdates: true)
// old style: self.layer.renderInContext(UIGraphicsGetCurrentContext())
let image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
}