ios - 在内存不足的情况下检索图像

Question

我正在尝试从用户的相机胶卷中检索图像，但遇到内存不足的问题。我一次加载 50 张图像，但不幸的是，加载几次后它会耗尽内存并崩溃。我试过将整个语句包装在一个自动释放池中，但事实证明这没有效果。这是我的代码...

func retrieveImages(thumbnail: Bool, indexOfLibrary: Int) {
    /* Retrieve the items in order of modification date, ascending */
    var indexSet: NSIndexSet!

    let options = PHFetchOptions()

    options.sortDescriptors = [NSSortDescriptor(key: "creationDate",
        ascending: false)]

    /* Then get an object of type PHFetchResult that will contain
    all our image assets */
    let assetResults = PHAsset.fetchAssetsWithMediaType(.Image,
        options: options)

    if totalPostsCounted == false {
        assetResults.enumerateObjectsUsingBlock { (object: AnyObject!, count: Int, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
            if object is PHAsset {
                self.totalPosts = count
            } else {
                self.totalPostsCounted = true
            }
        }
    }

    if thumbnail == true {
        if totalPosts - libraryImageThumbnails.count < 50 {
            allImagesLoaded = true
        } else {
            if firstTimeLoadedThumb == true {

            } else {
                firstTimeLoadedThumb = true

            }
        }

    } else {
        if totalPosts - libraryImages.count < 50 {
            allImagesLoaded = true
        } else {
            if firstTimeLoaded == true {
            } else {
                firstTimeLoaded = true

            }
        }


    }


    if thumbnail == true {
        fiftyIncrementThumb = fiftyIncrementThumb + 50
        increment = fiftyIncrementThumb
    } else {
        fiftyIncrement = fiftyIncrement + 50
        increment = fiftyIncrement
    }

    let imageManager = PHCachingImageManager()
    autoreleasepool { () -> () in

        assetResults.enumerateObjectsUsingBlock { (object, count: Int, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
            if object is PHAsset {

                var imageSize: CGSize!

                var array: NSArray!

                if thumbnail == true {
                    array = self.libraryImageThumbnails
                } else {
                    array = self.libraryImages
                }
                autoreleasepool {
                    if count >= array.count && count <= increment {
                        if thumbnail == true {
                            imageSize = CGSize(width: 100, height: 100)

                        } else {
                            imageSize = CGSize(width: self.cameraView.bounds.width, height: self.cameraView.bounds.height)

                        }

                        let asset = object as! PHAsset
                        let options = PHImageRequestOptions()
                        options.deliveryMode = .FastFormat
                        options.synchronous = true

                        imageManager.requestImageForAsset(asset,
                            targetSize: imageSize,
                            contentMode: .AspectFill,
                            options: options,
                            resultHandler: { (image, _: [NSObject : AnyObject]?) -> Void in
                                if thumbnail == true {
                                    self.libraryImageThumbnails.append(image!)
                                } else {
                                    self.libraryImages.append(image!)
                                }
                        })
                    }
                }
            }
        }


    }


}

我也试过这个，它返回 nil 并崩溃了......

    let library = ALAssetsLibrary()
        library.enumerateGroupsWithTypes(ALAssetsGroupAll, usingBlock: { (group: ALAssetsGroup!, stop: UnsafeMutablePointer<ObjCBool>) -> Void in

            group.enumerateAssetsUsingBlock({ (asset, count: Int, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
                if asset != nil {
                    self.libraryImageThumbnails.append(asset)
                    self.collectionTable.reloadData()

                }

            })
            }, failureBlock: { (error: NSError!) -> Void in

        })

如果您需要更多信息，请告诉我!谢谢!

Answer 1

以下是我在一个项目中所做的可能有帮助的事情:

一些属性:

let requestOptions = PHImageRequestOptions()
let fetchOptions = PHFetchOptions()
let cachingImageManager = PHCachingImageManager()
var assets: [PHAsset] = [] {
    willSet {
        cachingImageManager.stopCachingImagesForAllAssets()
    }

    didSet {
        cachingImageManager.startCachingImagesForAssets(assets,
            targetSize: PHImageManagerMaximumSize,
            contentMode: .AspectFit,
            options: self.requestOptions
        )
    }
}


func fetchPhotos() {
    requestOptions.resizeMode = PHImageRequestOptionsResizeMode.Exact
    requestOptions.version = .Current
    requestOptions.deliveryMode = PHImageRequestOptionsDeliveryMode.HighQualityFormat
    requestOptions.synchronous = true

    fetchOptions.sortDescriptors = [NSSortDescriptor(key:"creationDate", ascending: false)]
    if #available(iOS 9.0, *) {
        fetchOptions.fetchLimit = 50
    } else {

        // Fallback on earlier versions
    }

    fetchResults = PHAsset.fetchAssetsWithMediaType(PHAssetMediaType.Image, options: fetchOptions)
    guard let fetchResults = fetchResults else {
        print("No PHAssets")
        return
    }
    dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { [weak self] in
        fetchResults.enumerateObjectsUsingBlock{ object, index, stop in
            let asset = object as! PHAsset
            self?.assets.append(asset)
        }
        dispatch_async(dispatch_get_main_queue()) {
            self?.photoCollectionView.reloadData()
        }
    }
}