问题
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 I found on SO (since they all just directly pass it into say a tableview or something), but I have no success (likely because I'm not doing it right).
func getAssetThumbnail(asset: PHAsset) -> UIImage {
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(retimage)
return retimage
}
The printlns are telling me that the manager.request line isn't doing anything right now. How do I get it to give me the asset as a UIImage.
Thanks.
回答1:
This did what I needed it to do, in case anyone also needs this.
func getAssetThumbnail(asset: PHAsset) -> UIImage {
let manager = PHImageManager.defaultManager()
let option = PHImageRequestOptions()
var thumbnail = UIImage()
option.synchronous = true
manager.requestImageForAsset(asset, targetSize: CGSize(width: 100.0, height: 100.0), contentMode: .AspectFit, options: option, resultHandler: {(result, info)->Void in
thumbnail = result!
})
return thumbnail
}
Edit: Swift 3 update
func getAssetThumbnail(asset: PHAsset) -> UIImage {
let manager = PHImageManager.default()
let option = PHImageRequestOptions()
var thumbnail = UIImage()
option.isSynchronous = true
manager.requestImage(for: asset, targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFit, options: option, resultHandler: {(result, info)->Void in
thumbnail = result!
})
return thumbnail
}
回答2:
try this it works for me, hope it helps you too,
func getUIImage(asset: PHAsset) -> UIImage? {
var img: UIImage?
let manager = PHImageManager.default()
let options = PHImageRequestOptions()
options.version = .original
options.isSynchronous = true
manager.requestImageData(for: asset, options: options) { data, _, _, _ in
if let data = data {
img = UIImage(data: data)
}
}
return img
}
回答3:
Simple Solution (Swift 4.2)
Method 1:
extension PHAsset {
var image : UIImage {
var thumbnail = UIImage()
let imageManager = PHCachingImageManager()
imageManager.requestImage(for: self, targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFit, options: nil, resultHandler: { image, _ in
thumbnail = image!
})
return thumbnail
}
}
let image = asset.image
Use this method if you only need UIImage from PHAsset.
OR
extension PHAsset {
func image(targetSize: CGSize, contentMode: PHImageContentMode, options: PHImageRequestOptions?) -> UIImage {
var thumbnail = UIImage()
let imageManager = PHCachingImageManager()
imageManager.requestImage(for: self, targetSize: targetSize, contentMode: contentMode, options: options, resultHandler: { image, _ in
thumbnail = image!
})
return thumbnail
}
}
let image = asset.image(targetSize: CGSize, contentMode: PHImageContentMode, options: PHImageRequestOptions?)
Use this method for your desired UIImage.
OR
extension PHAsset {
func image(completionHandler: @escaping (UIImage) -> ()){
var thumbnail = UIImage()
let imageManager = PHCachingImageManager()
imageManager.requestImage(for: self, targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFit, options: nil, resultHandler: { img, _ in
thumbnail = img!
})
completionHandler(thumbnail)
}
}
let image = asset.image(completionHandler: {(img) in
print("Finished")
})
Use this method for notify after completion.
Method 2:
extension PHAsset {
var data : (UIImage, [AnyHashable : Any]) {
var img = UIImage(); var information = [AnyHashable : Any](); let imageManager = PHCachingImageManager()
imageManager.requestImage(for: self, targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFit, options: nil, resultHandler: { image,info in
img = image!
information = info!
})
return (img,information)
}
}
let image_withData : (UIImage, [AnyHashable : Any]) = asset.data
Use this method if you want UIImage And Result Info of PHAsset
OR
extension PHAsset {
func data(targetSize: CGSize, contentMode: PHImageContentMode, options: PHImageRequestOptions?) -> (UIImage, [AnyHashable : Any]) {
var img = UIImage(); var information = [AnyHashable : Any](); let imageManager = PHCachingImageManager()
imageManager.requestImage(for: self, targetSize: targetSize, contentMode: contentMode, options: options, resultHandler: { image,info in
img = image!
information = info!
})
return (img,information)
}
}
let data = asset?.data(targetSize: CGSize, contentMode: PHImageContentMode, options: PHImageRequestOptions?)
Use this method for your desired Data.
回答4:
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:
Create a PHCachingImageManager instance. (This step replaces using the shared PHImageManager instance.)
Use PHAsset class methods to fetch the assets you’re interested in.
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.
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)
回答5:
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
回答6:
Swift 4.
resizeMode,deliveryMode - These can be set according to user requirement.
isNetworkAccessAllowed - set this to "true" for fetching images from the cloud
imageSize- required image size
func getImageFromAsset(asset:PHAsset,imageSize:CGSize, callback:@escaping (_ result:UIImage) -> Void) -> Void{
let requestOptions = PHImageRequestOptions()
requestOptions.resizeMode = PHImageRequestOptionsResizeMode.fast
requestOptions.deliveryMode = PHImageRequestOptionsDeliveryMode.highQualityFormat
requestOptions.isNetworkAccessAllowed = true
requestOptions.isSynchronous = true
PHImageManager.default().requestImage(for: asset, targetSize: imageSize, contentMode: PHImageContentMode.default, options: requestOptions, resultHandler: { (currentImage, info) in
callback(currentImage!)
})
}
回答7:
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!
回答8:
Objective-c version of code based on dcheng answer.
-(UIImage *)getAssetThumbnail:(PHAsset * )asset {
PHImageRequestOptions *options = [[PHImageRequestOptions alloc]init];
options.synchronous = true;
__block UIImage *image;
[PHCachingImageManager.defaultManager requestImageForAsset:asset targetSize:CGSizeMake(100, 100) contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
image = result;
}];
return image;
}
来源：https://stackoverflow.com/questions/30812057/phasset-to-uiimage