LiveUseful is the first universal tool that inserts various hidden information into a Live Photo. Use these Live Photos, you can hide important things in your lock screen, and show them with 3D Touch.

See more details on App Store: LiveUseful - Make your lock screen useful!

There are some apps in the App Store copied my idea(a universal tool that inserts various hidden information into a Live Photo). I have killed some of them, but there are still some apps I can't take them off. Even Apple now decide not to reply to any mail from me. I really have no idea, so I decide to make my app opensource. I hope you can use my code to make a unique lock screen card for your app, or just run my code and have fun. ^_^

The core of LiveUseful is Live Photo。The App takes a screenshot of the view, then make a video from this image contain only one frame. Convert this video to Live Photo with a cover image as the background. When you press the screen with 3D Touch, it will start to play the video, display the image with hidden content. Because Live Photo has a built-in fade animation, the process will be very smooth.

A Live Photo is made from two parts: a JPEG image and a QuickTime video. You need to generate them separately then combine them as a Live Photo. And you also need to add some metadata to the files in order to join them together.

The video will be generated from a screenshot of the snapshotView. This view containing the background image and a card view above it.

To make this screenshot, you need to make a UIGraphicsImageContext. With drawHierarchy() function, you can get a screenshot of a view and ignore anything above it. In this case, I want the editing tools to be ignored.

UIGraphicsBeginImageContextWithOptions(targetSize, false, 1)
self.snapshotView.drawHierarchy(in: CGRect(origin: CGPoint.zero, size: targetSize), afterScreenUpdates: true)
let aImage = UIGraphicsGetImageFromCurrentImageContext()!.jpegData(compressionQuality: 1)!
sequenceImages.append(aImage)
UIGraphicsEndImageContext()

See "AddTextViewController.swift" to learn more.

For the image, you need to add some metadata to the file in order to link it with the video.

First, you need to generate a unique identifier. In my app, I use the UUID of the device.

Then set kCGImagePropertyMakerAppleDictionary to it. The dictionary now looks like: [17:assetIdentifier]. 17 means kFigAppleMakerNote_AssetIdentifier.

makerNote.setObject(assetIdentifier, forKey: kFigAppleMakerNote_AssetIdentifier as NSCopying)
metadata.setObject(makerNote, forKey: kCGImagePropertyMakerAppleDictionary as String as String as NSCopying)
CGImageDestinationAddImage(dest, image, metadata)

See "FileProcess/JPEG.swift" to learn more.

For the video, you need to pass a metadata adapter to the asset writer.

let spec : NSDictionary = [
           kCMMetadataFormatDescriptionMetadataSpecificationKey_Identifier as NSString:
           "\(kKeySpaceQuickTimeMetadata)/\(kKeyStillImageTime)",
           kCMMetadataFormatDescriptionMetadataSpecificationKey_DataType as NSString:
           "com.apple.metadata.datatype.int8"   

This app is using AVFoundation to generate video from images. To understand what's happening in this step, you may need to learn AVFoundation.

See "FileProcess/QuickTimeMov.swift" to learn more.

To make a Live Photo use for Live Photo view, you need to save the image and video to file first. Then you can pass the URL to PHLivePhoto.request() function.

PHLivePhoto.request(withResourceFileURLs: [imageURL, videoURL], placeholderImage: nil, targetSize: targetSize, contentMode: PHImageContentMode.aspectFit, resultHandler: { (livePhoto, info) -> Void in 
    doSomethingWithResult(livePhoto)
    print(info)
})

To make a Live Photo for saving, you need to do the same thing with PHAssetCreationRequest.forAsset() function.

let creationRequest = PHAssetCreationRequest.forAsset()
let options = PHAssetResourceCreationOptions()
creationRequest.addResource(with: PHAssetResourceType.photo, fileURL: self.imageURL, options: options)
creationRequest.addResource(with: PHAssetResourceType.pairedVideo, fileURL: self.videoURL, options: options)

Then save the file with PHPhotoLibrary.shared().performChanges() function.

See "BuildLivePhoto.swift" to learn more.

LiveUseful was designed using Sketch. You can download the .sketch file in the "Design" folder.

To support me, you can buy this app on App Store, or donate with WeChat or AliPay:

For app support, you can email to [email protected] .

LiveUseful is using MIT as open source license. But with an additional term: You could use part of the code, but do not upload this whole app to App Store by yourself.