How to convert PHAsset to UIImage in Objective-C

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.