如何在Objective-C中将PHAsset转换为UIImage

Question

我有一个充满PHAsset对象的数组(https://developer.apple.com/library/prerelease/ios/documentation/Photos/Reference/PHAsset_Class/index.html),我想知道如何将它们转换为UIImage然后将它们保存在一个数组中.

调用带有PHAsset对象的数组,self.assets这是我到目前为止所拥有的:

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是.h中的一个属性

@property (nonatomic, strong) PHImageRequestOptions *requestOptions;

并在viewDidLoad我这样做:

self.requestOptions = [[PHImageRequestOptions alloc] init];
self.requestOptions.resizeMode   = PHImageRequestOptionsResizeModeExact;
self.requestOptions.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;

但经过一些调试后,我一直看到它self.assets具有以下值:

(
<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 
)

并且images是空的.有谁知道如何添加将PHAssets转换为UIImages并将它们添加到images阵列？任何帮助表示赞赏.谢谢!

Answer 1

对于任何在这个问题上挣扎的人来说,这是要走的路.

首先将requestOptions设置为:

self.requestOptions = [[PHImageRequestOptions alloc] init];
self.requestOptions.resizeMode   = PHImageRequestOptionsResizeModeExact;
self.requestOptions.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;

// this one is key
self.requestOptions.synchronous = YES;

如果数组中有多个资源填充了PHAsset对象,则添加以下代码:

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];
                    }];


}

现在images数组包含uiimage格式的所有图像.