如何将图像保存到自定义相册？ [英] How to save image to custom album?

问题描述

我有一个全新的iOS应用程序，可以生成图像并让用户将它们保存到Camera SavedPhotosAlbum中。但是，我想做Snapchat和Frontback之类的东西，并将这些图像保存到自定义专辑中。

I have a brand new iOS app that generates images and lets the users save them into the Camera SavedPhotosAlbum. However, I wanna do something like Snapchat and Frontback, and save these images also to a custom-named album.

所以现在这是我的代码：

So this is my code right now:

let imageToSave = self.currentPreviewImage

let softwareContext = CIContext(options:[kCIContextUseSoftwareRenderer: true])
let cgimg = softwareContext.createCGImage(imageToSave, fromRect:imageToSave.extent())

ALAssetsLibrary().writeImageToSavedPhotosAlbum(cgimg, metadata:imageToSave.properties(), completionBlock:nil)

我见过几个人在Objective-C中这样做的例子，但我没有把它翻译成Swift，我检查了 writeImageToSavedPhotosAlbum 方法签名，但它们似乎都不允许保存到自定义相册。

I've seen a few examples of people doing this in Objective-C but nothing that I could translate to Swift, and I've check the writeImageToSavedPhotosAlbum method signatures and none of them seem to allow saving to a custom album.

推荐答案

我想出了这个单例类来处理它：

I came up with this singleton class to handle it:

import Photos

class CustomPhotoAlbum {

    static let albumName = "Flashpod"
    static let sharedInstance = CustomPhotoAlbum()

    var assetCollection: PHAssetCollection!

    init() {

        func fetchAssetCollectionForAlbum() -> PHAssetCollection! {

            let fetchOptions = PHFetchOptions()
            fetchOptions.predicate = NSPredicate(format: "title = %@", CustomPhotoAlbum.albumName)
            let collection = PHAssetCollection.fetchAssetCollectionsWithType(.Album, subtype: .Any, options: fetchOptions)

            if let firstObject: AnyObject = collection.firstObject {
                return collection.firstObject as! PHAssetCollection
            }

            return nil
        }

        if let assetCollection = fetchAssetCollectionForAlbum() {
            self.assetCollection = assetCollection
            return
        }

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({
            PHAssetCollectionChangeRequest.creationRequestForAssetCollectionWithTitle(CustomPhotoAlbum.albumName)
        }) { success, _ in
            if success {
                self.assetCollection = fetchAssetCollectionForAlbum()
            }
        }
    }

    func saveImage(image: UIImage) {

        if assetCollection == nil {
            return   // If there was an error upstream, skip the save.
        }

        PHPhotoLibrary.sharedPhotoLibrary().performChanges({
            let assetChangeRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
            let assetPlaceholder = assetChangeRequest.placeholderForCreatedAsset
            let albumChangeRequest = PHAssetCollectionChangeRequest(forAssetCollection: self.assetCollection)
            albumChangeRequest.addAssets([assetPlaceholder])
        }, completionHandler: nil)
    }


}

首次实例化课程时，如果自定义相册尚​​不存在，则会创建自定义相册。你可以保存这样的图像：

When you first instantiate the class, the custom album will be created if it doesn't already exist. You can save an image like this:

CustomPhotoAlbum.sharedInstance.saveImage(image)

注意：CustomPhotoAlbum类假定应用程序已拥有访问照片库的权限。处理权限有点超出了这个问题/答案的范围。因此，请在使用之前确保PHPhotoLibrary.authorizationStatus（）== .Authorize。并在必要时请求授权。

NOTE: The CustomPhotoAlbum class assumes the app already has permission to access the Photo Library. Dealing with the permissions is a bit outside the scope of this question/answer. So make sure PHPhotoLibrary.authorizationStatus() == .Authorize before you use it. And request authorization if necessary.

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