How to convert PHAsset to UIImage in Objective-C - ios

Question

I have an array filled with PHAsset objects (https://developer.apple.com/library/prerelease/ios/documentation/Photos/Reference/PHAsset_Class/index.html), and I want to know how I can convert them into a UIImage and then save them in an Array.
The array with the PHAsset objects is called self.assets and here is what I have so far:
PHImageManager *manager = [PHImageManager defaultManager];
CGFloat scale = UIScreen.mainScreen.scale;
NSMutableArray *images = [NSMutableArray arrayWithCapacity:[self.assets count]];
for (int i = 0; i < [self.assets count]; i++) {
CGSize targetSize = CGSizeMake(scale, scale);
[manager requestImageForAsset:[self.assets objectAtIndex:i]
targetSize:targetSize
contentMode:PHImageContentModeAspectFill
options:self.requestOptions
resultHandler:^(UIImage *image, NSDictionary *info){
[images addObject:image];
}];
}
self.requestOptions is a property in the .h
#property (nonatomic, strong) PHImageRequestOptions *requestOptions;
and in the viewDidLoad I am doing this:
self.requestOptions = [[PHImageRequestOptions alloc] init];
self.requestOptions.resizeMode = PHImageRequestOptionsResizeModeExact;
self.requestOptions.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
But after doing some debugging, I keep seeing that self.assets has the following values:
(
<PHAsset: 0x1743828a0> 3B6D658D-EC76-43A1-9793-35D889E9CF15/L0/001 mediaType=1/0, assetSource=3, (2448x2448), creationDate=2015-07-27 02:02:46 +0000, location=1, hidden=0, favorite=0 ,
<PHAsset: 0x174382970> 50F05575-71D2-446B-BD1E-8E3250E375AD/L0/001 mediaType=1/0, assetSource=3, (2448x2448), creationDate=2015-07-27 02:02:47 +0000, location=1, hidden=0, favorite=0
)
and images is empty. Does anyone know how I can add convert the PHAssets into UIImages and add them to the images array? Any help is appreciated. Thanks!

Answer 1

For anyone struggling as much as I had on this issue, this is the way to go.
First set the requestOptions as:
self.requestOptions = [[PHImageRequestOptions alloc] init];
self.requestOptions.resizeMode = PHImageRequestOptionsResizeModeExact;
self.requestOptions.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
// this one is key
self.requestOptions.synchronous = YES;
and if there are multiple assets in an array filled with PHAsset objects, then add this code:
self.assets = [NSMutableArray arrayWithArray:assets];
PHImageManager *manager = [PHImageManager defaultManager];
NSMutableArray *images = [NSMutableArray arrayWithCapacity:[assets count]];
// assets contains PHAsset objects.
__block UIImage *ima;
for (PHAsset *asset in self.assets) {
// Do something with the asset
[manager requestImageForAsset:asset
targetSize:PHImageManagerMaximumSize
contentMode:PHImageContentModeDefault
options:self.requestOptions
resultHandler:^void(UIImage *image, NSDictionary *info) {
ima = image;
[images addObject:ima];
}];
}
and now the images array contains all the images in uiimage format.

Answer 2

Swift 3.0 Answer
let photoAsset = asset
let manager = PHImageManager.default()
var options: PHImageRequestOptions?
options = PHImageRequestOptions()
options?.resizeMode = .exact
options?.isSynchronous = true
manager.requestImage(
for: photoAsset,
targetSize: PHImageManagerMaximumSize,
contentMode: .aspectFill,
options: options
) { [weak self] result, _ in
completion(result)
}
options?.isSynchronous = true is very important
BOOL synchronous; // return only a single result, blocking until available (or failure). Defaults to NO

Answer 3

image may be nil(seldom). It's better to evaluate, otherwise array add nil will crash app.
if(image){
ima = image;
[images addObject:ima];
}