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https://github.com/JanGorman/MapleBacon

🍁🥓 Lightweight and fast Swift library for image downloading, caching and transformations
https://github.com/JanGorman/MapleBacon

caching carthage cocoapods combine image image-download swift swift5 uiimageview xcode

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🍁🥓 Lightweight and fast Swift library for image downloading, caching and transformations

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# MapleBacon



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[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)

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# Introduction



MapleBacon is a lightweight and fast Swift library for downloading and caching images.



## Example



The folder `Example` contains a sample projects for you to try.



## Requirements



- Swift 5.1

- iOS 10.0+

- Xcode 10.2+



## Installation



MapleBacon is available through [CocoaPods](http://cocoapods.org). To install add it to your Podfile:



```ruby

pod "MapleBacon"

```



[Carthage](https://github.com/Carthage/Carthage)



```ogdl

github "JanGorman/MapleBacon"

```



and [Swift Package Manager](https://swift.org/package-manager).



## Usage



### UIImageView



The most basic usage is via an extension on `UIImageView`. You pass it URL:



```swift

import MapleBacon



private var imageView: UIImageView!



func someFunc() {

  let url = URL(string: "…")

  imageView.setImage(with: url)

}

```



If you want to add a placeholder while the image is downloading you specify that like this:



```swift

func someFunc() {

  let url = URL(string: "…")

  imageView.setImage(with: url, placeholder: UIImage(named: "placeholder"))

}

```



If your backend returns images that are not optimised for display, it's good practice to downsample them. MapleBacon comes with support for downsampling via `displayOptions`:



```swift

func someFunc() {

  let url = URL(string: "…")

  imageView.setImage(with: url, displayOptions: .downsampled)

}

```



### Image Transformers



MapleBacon allows you to apply transformations to images and have the results cached so that you app doesn't need to perform the same work over and over. To make your own transformer, create a class conforming to the `ImageTransforming` protocol. A transform can be anything you like, let's create one that applies a Core Image sepia filter:



```swift

private class SepiaImageTransformer: ImageTransforming {



  // The identifier is used as part of the cache key. Make sure it's something unique

  let identifier = "com.schnaub.SepiaImageTransformer"



  func transform(image: UIImage) -> UIImage? {

    let filter = CIFilter(name: "CISepiaTone")!



    let ciImage = CIImage(image: image)

    filter.setValue(ciImage, forKey: kCIInputImageKey)

    filter.setValue(0.5, forKey: kCIInputIntensityKey)



    let context = CIContext()

    guard let outputImage = filter.outputImage,

          let cgImage = context.createCGImage(outputImage, from: outputImage.extent) else {

            return image

    }



    // Return the transformed image which will be cached (or used by another transformer)

    return UIImage(cgImage: cgImage)

  }



}

```



You then pass this filter to MapleBacon in one of the convenience methods:



```swift

let url = URL(string: "…")

let transformer = SepiaImageTransformer()

imageView.setImage(with: url, transformer: transformer)

```



If you want to apply multiple transforms to an image, you can chain your transformers:



```swift

let chainedTransformer = SepiaImageTransformer()

  .appending(transformer: DifferentTransformer())

  .appending(transformer: AnotherTransformer())

```



Or if you prefer, using the custom `>>>` operator:



```swift

let chainedTransformer = SepiaImageTransformer() >>> DifferentTransformer() >>> AnotherTransformer()

```



(Keep in mind that if you are using Core Image it might not be optimal to chain individual transformers but rather create one transformer that applies multiple `CIFilter`s in one pass. See the [Core Image Programming Guide](https://developer.apple.com/library/content/documentation/GraphicsImaging/Conceptual/CoreImaging/ci_intro/ci_intro.html#//apple_ref/doc/uid/TP30001185).)



### Caching



MapleBacon will cache your images both in memory and on disk. Disk storage is automatically pruned after a week (taking into account the last access date as well) but you can control the maximum cache time yourself too:



```swift

let oneDaySeconds: TimeInterval = 60 * 60 * 24

MapleBacon.default.maxCacheAgeSeconds = oneDaySeconds

```



### Combine



On iOS13 and above, you can use `Combine` to fetch images from MapleBacon



```swift

MapleBacon.shared.image(with: url)

  .receive(on: DispatchQueue.main) // Dispatch to the right queue if updating the UI

  .sink(receiveValue: { image in

    // Do something with your image

  })

  .store(in: &subscriptions) // Hold on to and dispose your subscriptions

```



## Migrating from 5.x



There is a small [migration guide](https://github.com/JanGorman/MapleBacon/wiki/Migration-Guide-Version-5.x-→-6.x) in the wiki when moving from the 5.x branch to 6.x



## License



MapleBacon is available under the MIT license. See the LICENSE file for more info.