实体的模型定义：

实体的class定义：

@objc(ImageEntity)
class ImageEntity: NSManagedObject {
    @NSManaged var imageData: NSData
}

存储：

@IBAction func saveImageToCoreData() {
    let delegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context = delegate.managedObjectContext

    let imageData = UIImagePNGRepresentation(UIImage(named: "image"))

    let imageEntity = NSEntityDescription.entityForName("ImageEntity", inManagedObjectContext: context!)
    let image = ImageEntity(entity: imageEntity!, insertIntoManagedObjectContext: context!)
    image.imageData = imageData

    var error: NSError?
    if context!.save(&error) == false {
        println("failed: \(error!.localizedDescription)")
    }
}

读取：

@IBAction func loadImageFromCoreData() {
    let delegate = UIApplication.sharedApplication().delegate as AppDelegate
    let context = delegate.managedObjectContext

    let request = NSFetchRequest(entityName: "ImageEntity")
    var error: NSError?
    let imageEntities = context?.executeFetchRequest(request, error: &error)

    let imageEntity = imageEntities?.first! as ImageEntity
    self.imageView.image = UIImage(data: imageEntity.imageData)
}

Demo地址