PHAsset to UIImage

Question

I\'m attempting to create a UIImage (like a thumbnail or something) from a PHAsset so that I can pass it into something that takes a UIImage. I\'ve tried adapting solutions

Answer 1

I'd suggest using Apple's PHCachingImageManager (that inherits from PHImageManager):

A PHCachingImageManager object fetches or generates image data for photo or video assets

Also, PHCachingImageManager support a better caching mechanism.

Example of fetching a thumbnail synchronous:

let options = PHImageRequestOptions()
options.deliveryMode = .HighQualityFormat
options.synchronous = true // Set it to false for async callback

let imageManager = PHCachingImageManager()
imageManager.requestImageForAsset(YourPHAssetVar,
                                  targetSize: CGSizeMake(CGFloat(160), CGFloat(160)),
                                  contentMode: .AspectFill,
                                  options: options,
                                  resultHandler: { (resultThumbnail : UIImage?, info : [NSObject : AnyObject]?) in

                                                   // Assign your thumbnail which is the *resultThumbnail*
                                                  }

In addition, you can use PHCachingImageManager to cache your images for faster UI response:

To use a caching image manager:

1. Create a PHCachingImageManager instance. (This step replaces using the shared PHImageManager instance.)

2. Use PHAsset class methods to fetch the assets you’re interested in.

3. To prepare images for those assets, call the startCachingImagesForAssets:targetSize:contentMode:options: method with the target size, content mode, and options you plan to use when later requesting images for each individual asset.

4. When you need an image for an individual asset, call the requestImageForAsset:targetSize:contentMode:options:resultHandler: method, and pass the same parameters you used when preparing that asset.

If the image you request is among those already prepared, the PHCachingImageManager object immediately returns that image. Otherwise, Photos prepares the image on demand and caches it for later use.

In our example:

var phAssetArray : [PHAsset] = []

for i in 0..<assets.count
{
  phAssetArray.append(assets[i] as! PHAsset)
}

let options = PHImageRequestOptions()
options.deliveryMode = .Opportunistic
options.synchronous = false

self.imageManager.startCachingImagesForAssets(phAssetArray,
                                              targetSize: CGSizeMake(CGFloat(160), CGFloat(160)),
                                              contentMode: .AspectFill,
                                              options: options)

Answer 2

For Swift 3.0.1:

func getAssetThumbnail(asset: PHAsset, size: CGFloat) -> UIImage {
    let retinaScale = UIScreen.main.scale
    let retinaSquare = CGSize(width: size * retinaScale, height: size * retinaScale)//(size * retinaScale, size * retinaScale)
    let cropSizeLength = min(asset.pixelWidth, asset.pixelHeight)
    let square = CGRect(x:0, y: 0,width: CGFloat(cropSizeLength),height: CGFloat(cropSizeLength))
    let cropRect = square.applying(CGAffineTransform(scaleX: 1.0/CGFloat(asset.pixelWidth), y: 1.0/CGFloat(asset.pixelHeight)))

    let manager = PHImageManager.default()
    let options = PHImageRequestOptions()
    var thumbnail = UIImage()

    options.isSynchronous = true
    options.deliveryMode = .highQualityFormat
    options.resizeMode = .exact
    options.normalizedCropRect = cropRect

    manager.requestImage(for: asset, targetSize: retinaSquare, contentMode: .aspectFit, options: options, resultHandler: {(result, info)->Void in
        thumbnail = result!
    })
    return thumbnail
}

Resource : https://gist.github.com/lvterry/f062cf9ae13bca76b0c6#file-getassetthumbnail-swift

Answer 3

The problem is that requestImageForAsset is a resultHandler and this block of code happens in the future after your functions has already printed and returned the value you was expecting. I did come changes to show you this happening and also suggest some simple solutions.

func getAssetThumbnail(asset: PHAsset) {
    var retimage = UIImage()
    println(retimage)
    let manager = PHImageManager.defaultManager()
    manager.requestImageForAsset(asset, targetSize: CGSize(width: 100.0, height: 100.0), contentMode: .AspectFit, options: nil, resultHandler: {
    (result, info)->Void in
            retimage = result
      println("This happens after")
      println(retimage)
      callReturnImage(retimage) // <- create this method
    })
    println("This happens before")
}

Learn more about closures and completion handle and async funcs at Apple documentation

I hope that helps you!