Unable to load image from asset URL

You can't load images in this way.

You need to use ALAssetsLibrary class for this.

Add assetslibrary framework to your project and add header files.

Use the below code for loading image:

ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
{
    ALAssetRepresentation *rep = [myasset defaultRepresentation];
    CGImageRef iref = [rep fullResolutionImage];
    if (iref) {
        UIImage *largeimage = [UIImage imageWithCGImage:iref];
        yourImageView.image = largeImage;
    }
};

ALAssetsLibraryAccessFailureBlock failureblock  = ^(NSError *myerror)
{
    NSLog(@"Can't get image - %@",[myerror localizedDescription]);
};

NSURL *asseturl = [NSURL URLWithString:yourURL];
ALAssetsLibrary* assetslibrary = [[[ALAssetsLibrary alloc] init] autorelease];
[assetslibrary assetForURL:asseturl 
                   resultBlock:resultblock
                  failureBlock:failureblock];

Since iOS 8 you can use the Photos Framework here is how to do it in Swift 3

import Photos // use the Photos Framework

// declare your asset url
let assetUrl = URL(string: "assets-library://asset/asset.JPG?id=9F983DBA-EC35-42B8-8773-B597CF782EDD&ext=JPG")!

// retrieve the list of matching results for your asset url
let fetchResult = PHAsset.fetchAssets(withALAssetURLs: [assetUrl], options: nil)


if let photo = fetchResult.firstObject {

    // retrieve the image for the first result
    PHImageManager.default().requestImage(for: photo, targetSize: PHImageManagerMaximumSize, contentMode: .aspectFill, options: nil) {
        image, info in

        let myImage = image //here is the image
    }
}

Use PHImageManagerMaximumSize if you want to retrieve the original size of the picture. But if you want to retrieve a smaller or specific size you can replace PHImageManagerMaximumSize by CGSize(width:150, height:150)