//從網(wǎng)絡(luò)下載圖片
-(UIImage *) getImageFromURL:(NSString *)fileURL {
    NSLog(@"執(zhí)行圖片下載函數(shù)");
    UIImage * result;

    NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileURL]];
    result = [UIImage imageWithData:data];

    return result;
}

//將所下載的圖片保存到本地
-(void) saveImage:(UIImage *)image withFileName:(NSString *)imageName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    if ([[extension lowercaseString] isEqualToString:@"png"]) {
        [UIImagePNGRepresentation(image) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"png"]] options:NSAtomicWrite error:nil];
    } else if ([[extension lowercaseString] isEqualToString:@"jpg"] || [[extension lowercaseString] isEqualToString:@"jpeg"]) {
        [UIImageJPEGRepresentation(image, 1.0) writeToFile:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", imageName, @"jpg"]] options:NSAtomicWrite error:nil];
    } else {
        //ALog(@"Image Save Failed\\nExtension: (%@) is not recognized, use (PNG/JPG)", extension);
        NSLog(@"文件后綴不認識");
    }
}

//讀取本地保存的圖片
-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {
    UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]];

    return result;
}

//從網(wǎng)絡(luò)下載圖片，保存，并用 UIImageView 從保存中顯示
NSString * documentsDirectoryPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSLog(@"保存路徑:%@",documentsDirectoryPath);
    //Get Image From URL
    UIImage * imageFromURL = [self getImageFromURL:@"http://file.duteba.com/phone/2009/04/5/ftGxL8kcUL.jpg"];

    //Save Image to Directory
    [self saveImage:imageFromURL withFileName:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];

    //Load Image From Directory
    UIImage * imageFromWeb = [self loadImage:@"MyImage" ofType:@"jpg" inDirectory:documentsDirectoryPath];
    [img setImage:imageFromWeb];

    //取得目錄下所有文件名
    NSArray *file = [[[NSFileManager alloc] init] subpathsAtPath:documentsDirectoryPath];
    //NSLog(@"%d",[file count]);
    NSLog(@"%@",file);
//該片段來自于http://outofmemory.cn