iOS：从照片库中选择一个GIF，转换为NSData以用于multipart / form-data

Question

我的代码目前正在使用什么：

我从照片库中选择了JPG或PNG（使用标准的ImagePicker方法），并使用以下方法将该图像转换为NSData：

self.myImageData = UIImageJPEGRepresentation(myImage, 0.9); 

然后我使用multipart / form-data将其发布到服务器。

我现在想要为GIF做同样的事情，同时保留原始的GIF数据（以便动画GIF进入图书馆，恢复出来仍然是动画）。

在didFinishPickingMediaWithInfo中，我可以使用原始GIF的URL

self.myGIFURL = [info objectForKey:UIImagePickerControllerReferenceURL]. 

这是一个可能让我得到的例子：

资产库：//asset/asset.GIF ID = 1000000034＆EXT = GIF

以下是我现在尝试将此GIF推送到NSData的两种方法，每次myImageData显示（null）。

我试过使用initWithContentsOfURL：

NSData *dataFromGIFURL = [[NSData alloc] initWithContentsOfURL: myGIFURL];
self.myImageData = dataFromGIFURL;
[dataFromGIFURL release];

然后我尝试将NSURL转换为initWithContentsOfFile的字符串：

NSString *stringFromURL = [NSString stringWithFormat:@"%@", myGIFURL];
NSData *dataFromGIFURL = [[NSData alloc] initWithContentsOfFile: stringFromURL];
self.myImageData = dataFromGIFURL;
[dataFromGIFURL release];

有什么建议？ 谢谢。

Answer 1

UIImagePickerControllerReferenceURL键在iOS 4.1之前不会出现。 因此，我在你的问题中暗示，使用AssetsLibrary框架是很好的，该框架仅在4.0版本的iOS中出现。 在这种情况下，您可以使用以下内容：

- (void)imagePickerController:(UIImagePickerController *)picker 
        didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library assetForURL:[info objectForKey:UIImagePickerControllerReferenceURL]
        resultBlock:^(ALAsset *asset)
        {
            ALAssetRepresentation *representation = [asset defaultRepresentation];

            NSLog(@"size of asset in bytes: %d", [representation size]);

            unsigned char bytes[4];
            [representation getBytes:bytes fromOffset:0 length:4 error:nil];
            NSLog(@"first four bytes: %02x (%c) %02x (%c) %02x (%c) %02x (%c)",
                               bytes[0], bytes[0], 
                               bytes[1], bytes[1], 
                               bytes[2], bytes[2], 
                               bytes[3], bytes[3]);

            [library autorelease];
        }
        failureBlock:^(NSError *error)
        {
            NSLog(@"couldn't get asset: %@", error);

            [library autorelease];
        }
    ];
}

因此，您创建了一个ALAssetsLibrary，要求它找到指定了URL的资产（它理解assets-library：// URL方案），然后当您获得资产时，您将获取其默认表示并使用它来为您提供字节。 它们将是实际的磁盘上字节，来自磁带库的资产的默认表示形式是磁盘形式。

例如，选择我从Google图像中随机抓取的特定GIF，从连接到该代理的代理的图像选择器中获取输出：

2011-03-03 23：17：37.451 IPTest [1199：307]资产大小，以字节为单位：174960

2011-03-03 23:17:37.459 IPTest [1199：307]前四个字节：47（G）49（I）46（F）38（8）

这就是标准GIF标题的开头。 选择PNG或JPG可以识别PNG和JPG标头的前四个字节。

编辑：完成这个想法，显然你可以使用ALAssetRepresentation将描述文件的所有字节读入一个适当的malloc'd C数组，然后使用NSData +（id）dataWithBytes：length :(或者更可能的是，+ dataWithBytesNoCopy： length：freeWhenDone :)将其包装成NSData。

Answer 2

这是一个使用较新的Photos框架的版本：

- (void) imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    NSURL * refUrl = [info objectForKey:UIImagePickerControllerReferenceURL];
    if (refUrl) {
        PHAsset * asset = [[PHAsset fetchAssetsWithALAssetURLs:@[refUrl] options:nil] lastObject];
        if (asset) {
            PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
            options.synchronous = YES;
            options.networkAccessAllowed = NO;
            options.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
            [[PHImageManager defaultManager] requestImageDataForAsset:asset options:options resultHandler:^(NSData * _Nullable imageData, NSString * _Nullable dataUTI, UIImageOrientation orientation, NSDictionary * _Nullable info) {
                NSNumber * isError = [info objectForKey:PHImageErrorKey];
                NSNumber * isCloud = [info objectForKey:PHImageResultIsInCloudKey];
                if ([isError boolValue] || [isCloud boolValue] || ! imageData) {
                    // fail
                } else {
                    // success, data is in imageData
                }
            }];
        }
    }
}

Answer 3

这是使用Swift 3的Eli版本：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String: Any]) {
    guard let imageURL = info[UIImagePickerControllerReferenceURL] as? URL else { return }
    guard let asset = PHAsset.fetchAssets(withALAssetURLs: [imageURL], options: nil).lastObject else { return }

    if picker.sourceType == .photoLibrary || picker.sourceType == .savedPhotosAlbum {
        let options = PHImageRequestOptions()
        options.isSynchronous = true
        options.isNetworkAccessAllowed = false
        options.deliveryMode = .highQualityFormat
        PHImageManager.default().requestImageData(for: asset, options: options) { data, uti, orientation, info in
            guard let info = info else { return }

            if let error = info[PHImageErrorKey] as? Error {
                log.error("Cannot fetch data for GIF image: \(error)")
                return
            }

            if let isInCould = info[PHImageResultIsInCloudKey] as? Bool, isInCould {
                log.error("Cannot fetch data from cloud. Option for network access not set.")
                return
            }

            // do something with data (it is a Data object)
        }
    } else {
        // do something with media taken via camera
    }
}

Answer 4

Swift 4更新：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    let mediaType = info[UIImagePickerControllerMediaType] as! CFString
    let assetPath = info[UIImagePickerControllerReferenceURL] as! URL

    self.dismiss(animated: true, completion: nil)
    switch mediaType {
        case kUTTypeImage, kUTTypeLivePhoto, kUTTypeGIF:
            if let selectedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
                if (assetPath.absoluteString.hasSuffix("GIF")) || (assetPath.absoluteString.hasSuffix("gif")){
                    print("GIF")
                    let options = PHImageRequestOptions()
                    options.isSynchronous = true
                    options.isNetworkAccessAllowed = false
                    options.deliveryMode = .highQualityFormat

                    guard let asset = PHAsset.fetchAssets(withALAssetURLs: [assetPath], options: nil).lastObject else { return }
                    PHImageManager.default().requestImageData(for: asset, options: options) { data, uti, orientation, info in
                    guard let info = info else { return }

                    if let error = info[PHImageErrorKey] as? Error {
                        print("Cannot fetch data for GIF image: \(error)")
                        return
                    }

                    if let isInCould = info[PHImageResultIsInCloudKey] as? Bool, isInCould {
                       print("Cannot fetch data from cloud. Option for network access not set.")
                        return
                    }
                    if let gifImageData = data {
                        // do something with data (it is a Data object)
                    }
                }
            } else {
                // this is the basic image 
            }
        }
        case kUTTypeMovie:
            if let videoURL = info[UIImagePickerControllerMediaURL] as? URL {
                // using video type
            }
        default:
            print("Others")
        }
    }