Save image in NSUserDefaults [closed] - ios

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I need to store and retrieve images in my app, I first thought of doing it like so:
[[NSUserDefaults standardUserDefaults] setObject:UIImagePNGRepresentation(image) forKey:key];
NSData* imageData = [[NSUserDefaults standardUserDefaults] objectForKey:key];
UIImage* image = [UIImage imageWithData:imageData];
But I read this isn't the recommended way. What is the best approach for this?
(I know there are duplicates of this question, but I haven't understood how to do it yet)

Answer 1

The best way to store images depends on what your app does.
If you have 100k+ images you probably want to save it manually to the iphone's hard disk over coredata since it will load images faster this way.
However, if you have less than that, then storing images as binary data in core data is what I would recommend.
The benefits of using coredata vs the file system:
Better iCloud Sync Support
No need to manage images on the hard disk as well as what ever you use as a 'persistence store' (coredata/nsuserdefaults/custom)
You can tie images to other data such as name, created date, ect.
Some interesting performance info with filesystem vs coredata: http://biasedbit.com/filesystem-vs-coredata-image-cache/

Answer 2

You'd have to take the data from UIImageJPEGRepresentation() and store it in an NSData object or some such in order for it to be "plist-serializable" to store in NSUserDefaults, but as others have said, you're much better off storing the image as an image file on the file system somewhere and storing the file path or file URL in NSUserDefaults.

Answer 3

Save the image in the Documents directory, then save the file name in a database (Core Data perhaps), another file format or NSUserDefaults.
NSUserDefaults is not really a great way to store app data.
From a UIImage instance get the data with
UIImagePNGRepresentation() or UIImageJPEGRepresentation(). Then save the data to a file. Use imageWithContentsOfFile: to recover the UIImage.
To obtain the path to the documents directory:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths firstObject];

Answer 4

The easiest way for you is to directly save the content to your iOS Device and store the path in the NSUserDefaults.
First convert the image to a file and save it to the phone.
UIImage *image = // your image
NSData *pngImageData = UIImagePNGRepresentation(image);
NSArray *paths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths firstObject];
NSString *fileName = [NSString stringWithFormat:#"%#/imageName.png",
documentsDirectory];
[pngImageData writeToFile:fileName atomically:YES];
Some are against storing filePaths in NSUserDefaults because, you're not suppose to store anything in NSUserDefaults that is super dynamic, you're suppose to store things like session keys, or token values, user names even, things that don't change often or are very strict.
The suggestion is, if you absolutely refuse CoreData, to make a property list and store the string name there.
To store your imagePath in a plist you would do the following:
NSString *textPath = [[NSBundle mainBundle] pathForResource:#"propertyListName" ofType:#"plist"];
NSDictionary *thisDict = [NSDictionary dictionaryWithContentsOfFile:textPath];
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:thisDict];
mutableDictionary[#"key"] = fileName;
[mutableDictionary writeToFile:resultsPath atomically:YES];
To retrieve your image from a plist you would do the following
NSString *textPath = [[NSBundle mainBundle] pathForResource:#"propertyListName" ofType:#"plist"];
NSDictionary *thisDict = [NSDictionary dictionaryWithContentsOfFile:textPath];
NSString *imagePath = thisDict[#"key"];
NSData *imageData = [NSData dataWithContentsOfFile:filePath];
UIImage *myImage = [UIImage imageWithData:imageData];
Do not use this NSUserDefaults option for it is wrong, but if you wanted to, this is how you would do it.
[[NSUserDefaults standardUserDefaults] setObject:fileName forKey:#"key"];
[[NSUserDefaults standardUserDefaults] synchronize];
now it's saved easily for you to retrieve. When you want to retrieve the image.
NSString *filePath = [[NSUserDefaults standardUserDefaults] objectForKey:#"key"];
NSData *imageData = [NSData dataWithContentsOfFile:filePath];
UIImage *myImage = [UIImage imageWithData:imageData];
then use myImage as the image. Remember the key must be the same when setting and retrieving.
The best way to store images depends on what your app does.
If you have 100k+ images you probably want to save it manually to the iphone's hard disk over coredata since it will load images faster this way.
However, if you have less than that, then storing images as binary data in core data is what I would recommend.
The benefits of using coredata vs the file system:
Better iCloud Sync Support
No need to manage images on the hard disk as well as what ever you use as a 'persistence store' (coredata/nsuserdefaults/custom)
You can tie images to other data such as name, created date, ect.
Some interesting performance info with filesystem vs coredata: http://biasedbit.com/filesystem-vs-coredata-image-cache/