Simple and efficient image lazy loading functionality for the iOS written in Swift.

LazyImage offers ease of use and complete control over your images by integrating a very light, need-to-have only, code.

Features

• Asynchronous image downloader on a background thread. Main thread is never blocked.

• Instance based for better unit testing your code.

• Temporary caching of the downloaded images with automatic OS clean up.

• Set a local project image as a placeholder or a spinner until the actual image is available

• If the imageView's size is 0, it sets dimensions to 40x40 prior to the request. This applies to the default UITableViewCells due to the fact when no initial image is present the imageView is hidden.

Complete control over your image data

• Guarantees that the same image url will not be downloaded again but will be fetched from the cache.

• Option for force downloading the same image overriding the cache.

• Option for clearing images from the cache which correspond to specific URLs so they can be re-downloaded once,

instead of force downloading them continuously.

• Notifies the caller when the operation is complete providing descriptive error if any.

• Image can be scaled automatically to your specific view dimensions for best performance and reduced memory allocation.

• Set the cache image size ratio for saving images. Display them super fast 🚀.

Installation - Cocoapods

pod 'LazyImage'

Usage

LazyImageView

The simplest way to show an image on an image view is by setting the type to LazyImageView and setting the imageURL property.

The downloaded image will be cached to your image view size for best performance.

Example:

@IBOutlet weak var imageView: LazyImageView!

//Normal image

imageview.image = UIImage(named:"someAsset")

//Network image

imageView.imageURL = "https://domain.com/thepathtotheimage.png"

//Option to cancel the request

let canceled = imageView.cancelRequest()

In case you want to know if the image fails to be retrieved.

Use the LazyImageViewDelegate.

@IBOutlet weak var imageView: LazyImageView!

imageView.delegate = <your delegate target with conforms to LazyImageViewDelegate>

//Set the image URL

imageView.imageURL = "https://domain.com/thepathtotheimage.png"


//If an error occurs this will be called

//url is the image URL failed to be fetched.

func errorDownloadingImage(url:String) -> Void {
}

LazyImage

For complete control you can use the LazyImage object on any UIImageview.

Below are some exampes of loading images

• Show an image on an imageView

Create a lazy image object that will hold the instance.

It is best that you create one instance per object responsible for the image

lazy var lazyImage:LazyImage = LazyImage()

Without completion closure

self.lazyImage.show(imageView:self.imageView, url:"http://something.com/someimage.png")

With spinner

self.lazyImage.showWithSpinner(imageView:self.imageView, url:"http://something.com/someimage.png")

With completion closure

self.lazyImage.show(imageView:self.imageView, url:"http://something.com/someimage.png") {

(error:LazyImageError?) in

//Image loaded. Do something..
}

self.lazyImage.showWithSpinner(imageView:self.imageView, url:"http://something.com/someimage.png") {

(error:LazyImageError?) in

//Image loaded. Do something..
}

• Show an image with a local image placeholder

With completion

self.lazyImage.show(imageView:self.imageView, url:"http://something.com/someimage.png", defaultImage:"someLocalImageName") {

(error:LazyImageError?) in

//Image loaded. Do something..
}

• Show an image with scaled size for better performance

With spinner and new scaled size. Image is resized for your desired size for maximum performance

let newSize = CGSize(width: imageViewWidth height: imageViewHeight)

self.lazyImage.showWithSpinner(imageView:self.imageView, url:"http://something.com/someimage.png", size:newSize) {

(error:LazyImageError?) in

//Image loaded. Do something..
}

• Force download an image with scaled size even if it is stored in cache

Sometimes a specific URL can constantly change the corresponding image.

With completion

let newSize = CGSize(width: imageViewWidth height: imageViewHeight)

self.lazyImage.showOverride(imageView:self.imageView, url:"http://something.com/someimage.png", size:newSize) {

(error:LazyImageError?) in

//Image loaded. Do something..
}

With completion, spinner and new scaled size

let newSize = CGSize(width: imageViewWidth height: imageViewHeight)

self.lazyImage.showOverrideWithSpinner(imageView:self.imageView, url:"http://something.com/someimage.png", size:newSize) {

(error:LazyImageError?) in

//Image loaded. Do something..
}

Dealing with the image size and the cache

In general showing an image optimized for your view dimensions is the best approach for optimal memory handling . You can achieve this in 2 ways.

• Using the size parameter as shown in the above examples. The size will be used to scale down the image for your specific size. This will happen on the fly, which means the original image is stored in the cache. Resizing will be performed upon load. Resizing/ image loading happens in a background thread, UI is never blocked. Main thread is for displaying only.

let newSize = CGSize(width: imageViewWidth height: imageViewHeight)

self.lazyImage.showWithSpinner(imageView:self.imageView, url:"http://something.com/someimage.png", size:newSize) {

(error:LazyImageError?) in

//Image loaded. Do something..
}

• Setting the cache size is the second option. Valid as long as your instance is alive, this will cause the images to be stored resized in the cache. Loading your fresh resized images for you specific dimensions will be super fast 🚀.

let imageSize = CGSize(width: yourViewWidth, height: yourViewHeight)



//Set default image size ratio

self.lazyImage.setCacheSize(imageSize)



self.lazyImage.showWithSpinner(imageView:self, url:imageURL) {

(error:LazyImageError?)  in

}

Clearing the cache for specific image URLs

Sometimes you just need to re-download a specific image with the exact same name once.

If you have a cache size set, clearing the cache will clear images of the specific size ratio.

Clearing the cache:

let imageURLs:[String] = ["https://someimage.png", "https://someotherimage.png"]

self.lazyImage.clearCacheForURLs(urls: urls)

//And you're done

Prefetching

You can prefetch an image and save it to be ready for fast displaying.

self.lazyImage.prefetchImage(url: "https://someimage.png")

Forget UIImageviews. Just get the UIImage

self.lazyImage.fetchImage(url: url) {

(image:UIImage?, error:LazyImageError?) in

//image has the UIImage

}

Cancel the image fetching request

self.lazyImage.cancel()

Contributing

Contributions are welcomed. Fork the project and make it better, then create a pull request. The project comes with a very basic target app for testing your new features. You can find the library code under Pods/Development Pods/LazyImage.

License

Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0