Question

我试图用内置相机拍照后为JPEG个文件（例如MD5）计算文件哈希。我可以在图像数据上创建摘要，但这与实际的文件哈希不同。在查看Photo模块及其PHAsset类时，我没有找到一种方法来检索实际的文件路径（URL），然后可以将其馈送到MD5Digest。通过实现完成侦听器功能，也许可以在将图像保存到相机胶卷之后立即捕获文件URL。有人尝试过吗？

使用completionHandler更新了代码，但是我仍然需要查找URL。

 @IBOutlet weak var imageHash: UILabel!

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

    let orgPic = info[UIImagePickerController.InfoKey.originalImage] as? UIImage

    UIImageWriteToSavedPhotosAlbum(orgPic!, self, #selector(imageSaved(_:didFinishSavingWithError:contextInfo:)), nil)

}

@objc func imageSaved(_ img: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
        if let error = error {
            // we got back an error!
            let ac = UIAlertController(title: "Save error", message: error.localizedDescription, preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        } else {
            let ac = UIAlertController(title: "Saved!", message: "\(img.ciImage?.url)", preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        }
 }

// the img.ciImage.url is "nil" unfortunately

Answer 1

因此，您的主要座右铭是比较2个Image文件的MD5。所以这是我尝试过的，也许会对您有所帮助

; TLDR-保存在“库”中的文件与实际文件对我不匹配

 public func saveImgToLocal(_ img: UIImage,
                           onComplete: @escaping () -> Void) {

    var blockPlaceholder: PHObjectPlaceholder?
    var changeRequest: PHAssetChangeRequest?

    PHPhotoLibrary.shared().performChanges({
        changeRequest =  PHAssetChangeRequest.creationRequestForAsset(from: img)
        blockPlaceholder = changeRequest?.placeholderForCreatedAsset
    }, completionHandler: { (saved, error) in
        //_saved_ is of type bool, you can use it to check whether image is saved
        //Here we would fetch the asset using our saved placeholder
        let fetchOptions = PHFetchOptions()
        let fetchResult:PHFetchResult = PHAsset.fetchAssets(withLocalIdentifiers: [blockPlaceholder!.localIdentifier], options: fetchOptions)
        if let asset = fetchResult.firstObject {
            //Method to convert asset to Actual image
            self.getAsset(asset: asset)
        }
        onComplete()

    })
}

这就是我将图像保存到本地的方式

这就是我从本地获取图片的方式

func getAsset(asset: PHAsset)  {
    let manager = PHImageManager.default()
    let option = PHImageRequestOptions()
    var resultImage = UIImage()
    option.isSynchronous = true
    manager.requestImage(for: asset, targetSize: PHImageManagerMaximumSize, contentMode: .aspectFit, options: option, resultHandler: {(result, info)->Void in
        resultImage = result!
        let url = info!["PHImageFileURLKey"] as! NSURL
        //Image created using the file URL.
        let image = UIImage.init(contentsOfFile: url.path!)
//I even compared the resultImage instead of the image from the file
        if UIImagePNGRepresentation(image!) == UIImagePNGRepresentation(self.image!) {
            print("Same image")
        }
    })

}

因此，如果您只想找回保存的图像，可以这样做，但是我不确定图像是否按原样保存在照片库中。 HTH：-）

Answer 2

尽管Ajinkya Sharma发布的代码可行，但我注意到与UIImageWriteToSavedPhotosAlbum相比，使用creationRequestForAsset将图像保存到相机胶卷的性能明显降低。因此，我选择了一种混合解决方案。我使用旧函数进行保存，然后使用PHAsset框架获取最新的图像文件并检索其URL。问题解决了。

public func saveImgToLocal(_ img: UIImage) {
    // significantly faster than creationRequestForAsset
    UIImageWriteToSavedPhotosAlbum(img, self, #selector(imageSaved(_:didFinishSavingWithError:contextInfo:)), nil)
}

@objc func imageSaved(_ img: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
    if let error = error {
        // we got back an error!
        let ac = UIAlertController(title: "Save error", message: error.localizedDescription, preferredStyle: .alert)
        ac.addAction(UIAlertAction(title: "OK", style: .default))
        present(ac, animated: true)
    } else {
        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
        fetchOptions.fetchLimit = 1
        let fetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
        if let asset = fetchResult.firstObject
        {
            self.imageHash.text = getAsset(asset: asset)
        }
    }
}

func getAsset(asset: PHAsset) -> String {
    let manager = PHImageManager.default()
    let option = PHImageRequestOptions()
    var hashString = "" as String
    option.isSynchronous = true
    manager.requestImage(for: asset, targetSize: PHImageManagerMaximumSize, contentMode: .aspectFit, options: option, resultHandler: {(result, info) -> Void in
        let url = info!["PHImageFileURLKey"] as! NSURL
        do {
            let data = try Data(contentsOf: url as URL)
            hashString = data.md5.rawValue
        }
        catch {
            hashString = "Error computing hash"
        }
    })
    return hashString
}

文件访问相机胶卷上的图像文件（iOS 12.1.4，Swift 4.2，Xcode 10.1）

2 个答案: