在不耗尽内存的情况下检索图像

Posted 2023-03-08

【中文标题】在不耗尽内存的情况下检索图像

【英文标题】：Retrieve Images Without Running Out Of Memory

【发布时间】：2016-01-26 05:54:11

【问题描述】：

我正在尝试从用户的相机胶卷中检索图像，但遇到了内存不足的问题。我一次加载 50 张图像，但不幸的是，在几次加载后，它会耗尽内存并崩溃。我尝试将整个语句包装在自动释放池中，但事实证明这并不有效。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！

【问题讨论】：

您需要做的是获取图像的 url，然后使用来自该 url 的dispatch_async 将图像加载到后台队列中。

@DhaivatVyas 如何使用文件 URL 从我的相机胶卷中检索图像？

【参考方案1】：

这是我在一个项目中所做的可能会有所帮助的事情：

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()
        
    

【讨论】：

太棒了。乐于助人！

【参考方案2】：

试试这段代码，确保你导入<AssetsLibrary/AssetsLibrary.h>，并将你的部署目标设为7.1。

Objective-C 代码

NSMutableArray *imageArray=[[NSMutableArray alloc] init];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

[library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop)


    [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop)
     
         if (asset) 
             [imageArray addObject:asset];
             NSLog(@"imageArray :: %@",imageArray);
         
     ];
 failureBlock:^(NSError *error) 
    NSLog(@"error :: %@",error);
];

Swift 代码

var imageArray: [AnyObject] = [AnyObject]()
var library: ALAssetsLibrary = ALAssetsLibrary()

   library.enumerateGroupsWithTypes(ALAssetsGroupSavedPhotos, usingBlock: (group: ALAssetsGroup, stop: Bool) -> Void in
    group.enumerateAssetsUsingBlock((asset: ALAsset, index: Int, stop: Bool) -> Void in
        if asset != nil 
            imageArray.append(asset)
            NSLog("imageArray :: %@", imageArray)
        
   )
, failureBlock: (error: NSError) -> Void in
NSLog("error :: %@", error!)
)

结果：

查看以下网址以供参考

https://***.com/a/15570221/4101371

https://***.com/a/25732673/4101371

https://***.com/a/32472476/4101371

您还可以使用 iOS 8 及更高版本的照片框架。 photos Framework

希望它会有所帮助。

【讨论】：

我刚刚尝试了其中一个建议，并编辑了我的问题以显示我这样做时发生了什么。

嗯，由于某种原因，当我尝试它可以工作时，但是当我尝试在 cellForRow 中设置图像时它崩溃了。

【参考方案3】：

设置下面的代码对我来说可以限制获取

let assetFetchOptions = PHFetchOptions()
assetFetchOptions.fetchLimit = 50

然后我只检索到 50 张照片，而我朋友的手机上只有 15,000 张！！