iOS 根据图片URL从本地相册获取图片

最近做一个聊天的项目，需要发送图片后读取本地图片显示到列表里。刚开始的时候，天真的认为可以用SDWebImage直接加载，然后并不能行。

于是在网上搜了搜，如何根据从相册获取的UIImagePickerControllerReferenceURL读取图片， 代码如下：

#import "ViewController.h"
#import <AssetsLibrary/AssetsLibrary.h>

@interface ViewController ()<UINavigationControllerDelegate, UIImagePickerControllerDelegate>
- (IBAction)showImagePickerVC:(id)sender;
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];   
}

 弹出图片选择器

- (IBAction)showImagePickerVC:(id)sender {
    
    UIImagePickerController *imagePickerVC = [[UIImagePickerController alloc] init];
    
    imagePickerVC.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    imagePickerVC.allowsEditing = YES;
    
    imagePickerVC.delegate = self;
    
    [self presentViewController:imagePickerVC animated:YES completion:nil];
    
}

 回调

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSLog(@"%@", info);
    NSURL *imagePath = info[@"UIImagePickerControllerReferenceURL"];

    if ([[[imagePath scheme] lowercaseString] isEqualToString:@"assets-library"]) {
        
        // Load from asset library async
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            @autoreleasepool {
                @try {
                    ALAssetsLibrary *assetslibrary = [[ALAssetsLibrary alloc] init];
                    [assetslibrary assetForURL:imagePath
                                   resultBlock:^(ALAsset *asset){
                                       ALAssetRepresentation *rep = [asset defaultRepresentation];
                                       CGImageRef iref = [rep fullScreenImage];
                                       if (iref) {
                                           //进行UI修改
                                           dispatch_sync(dispatch_get_main_queue(), ^{
                                               _imageView.image = [[UIImage alloc] initWithCGImage:iref];
                                           });
                                           
                                        }
                
                                   }
                                  failureBlock:^(NSError *error) {
                                      
                                      NSLog(@"从图库获取图片失败: %@",error);
                                      
                                  }];
                } @catch (NSException *e) {
                    NSLog(@"从图库获取图片异常: %@", e);
                }
            }
        });
        
    }
    
    [picker dismissViewControllerAnimated:YES completion:nil];
}