【发布时间】：2012-02-10 15:43:57
【问题描述】：
我见过其他应用程序这样做，您可以从“照片”应用程序导入最后一张照片以供快速使用，但据我所知，我只知道如何获取 A 图像而不是最后一张（最近的一张）。谁能告诉我如何获取最后一张图片？
【问题讨论】：
【发布时间】：2012-02-10 15:43:57
【问题描述】：
好吧，这里有一个解决方案，如何使用 Swift 3 人从图库中加载最后一张图片：
func loadLastImageThumb(completion: @escaping (UIImage) -> ()) {
let imgManager = PHImageManager.default()
let fetchOptions = PHFetchOptions()
fetchOptions.fetchLimit = 1
fetchOptions.sortDescriptors = [NSSortDescriptor(key:"creationDate", ascending: true)]
let fetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
if let last = fetchResult.lastObject {
let scale = UIScreen.main.scale
let size = CGSize(width: 100 * scale, height: 100 * scale)
let options = PHImageRequestOptions()
imgManager.requestImage(for: last, targetSize: size, contentMode: PHImageContentMode.aspectFill, options: options, resultHandler: { (image, _) in
if let image = image {
completion(image)
}
})
}
}
如果您需要更快的速度，您也可以使用PHImageRequestOptions 并设置这些：
options.deliveryMode = .fastFormat
options.resizeMode = .fast
这就是你在 viewController 中获取它的方式（你应该用你的类替换 GalleryManager.manager）：
GalleryManager.manager.loadLastImageThumb { [weak self] (image) in
DispatchQueue.main.async {
self?.galleryButton.setImage(image, for: .normal)
}
}
【讨论】：
这是 Swift 中的一个版本，它请求数据并将其转换为 UIImage，因为提供的版本每次都返回一个空的 UIImage
let fetchOptions = PHFetchOptions()
fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: true)]
let fetchResult = PHAsset.fetchAssetsWithMediaType(PHAssetMediaType.Image, options: fetchOptions)
if let lastAsset: PHAsset = fetchResult.lastObject as? PHAsset {
let manager = PHImageManager.defaultManager()
let imageRequestOptions = PHImageRequestOptions()
manager.requestImageDataForAsset(lastAsset, options: imageRequestOptions) {
(let imageData: NSData?, let dataUTI: String?,
let orientation: UIImageOrientation,
let info: [NSObject : AnyObject]?) -> Void in
if let imageDataUnwrapped = imageData, lastImageRetrieved = UIImage(data: imageDataUnwrapped) {
// do stuff with image
}
}
}
【讨论】：
以下代码适用于 iOS7 和 iOS8。它还检查过滤器中是否有图像。在执行代码之前，您应该检查相册权限：
// get the latest image from the album
-(void)getLatestPhoto
{
NSLog(@"MMM TGCameraViewController - getLatestPhoto");
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
// Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.
[library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
// Within the group enumeration block, filter to enumerate just photos.
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
// For this example, we're only interested in the last item [group numberOfAssets]-1 = last.
if ([group numberOfAssets] > 0) {
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:[group numberOfAssets]-1]
options:0
usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {
// The end of the enumeration is signaled by asset == nil.
if (alAsset) {
ALAssetRepresentation *representation = [alAsset defaultRepresentation];
// Do something interesting with the AV asset.
UIImage *img = [UIImage imageWithCGImage:[representation fullScreenImage]];
// use the photo here ...
// we only need the first (most recent) photo -- stop the enumeration
*innerStop = YES;
}
}];
}
}
failureBlock: ^(NSError *error) {
// Typically you should handle an error more gracefully than this.
NSLog(@"No groups");
}];
}
（此代码是here的修改版。）
【讨论】：
此代码 sn-p 将从相机胶卷中获取最新图像（iOS 7 及以下）：
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
// Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.
[library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
// Within the group enumeration block, filter to enumerate just photos.
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
// Chooses the photo at the last index
[group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {
// The end of the enumeration is signaled by asset == nil.
if (alAsset) {
ALAssetRepresentation *representation = [alAsset defaultRepresentation];
UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullScreenImage]];
// Stop the enumerations
*stop = YES; *innerStop = YES;
// Do something interesting with the AV asset.
[self sendTweet:latestPhoto];
}
}];
} failureBlock: ^(NSError *error) {
// Typically you should handle an error more gracefully than this.
NSLog(@"No groups");
}];
iOS 8 及更高版本：
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
PHFetchResult *fetchResult = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions];
PHAsset *lastAsset = [fetchResult lastObject];
[[PHImageManager defaultManager] requestImageForAsset:lastAsset
targetSize:self.photoLibraryButton.bounds.size
contentMode:PHImageContentModeAspectFill
options:PHImageRequestOptionsVersionCurrent
resultHandler:^(UIImage *result, NSDictionary *info) {
dispatch_async(dispatch_get_main_queue(), ^{
[[self photoLibraryButton] setImage:result forState:UIControlStateNormal];
});
}];
【讨论】：
-
注意：如果相机胶卷中没有照片，此代码将崩溃。在现实世界中不常见，但仍然是您想要检查的东西。我在第一个块级别中添加了
if ([group numberOfAssets] < 1) return;来防御这种情况。 -
@iBradApps
enumerateAssetsAtIndexes:options:usingBlock:已替换为enumerateAssetsWithOptions:usingBlock:和选项NSEnumerationReverse。添加了使用stop和innerStop布尔变量，因此一旦找到资产，我们仍将停止枚举。您可以在stackoverflow.com/posts/8872425/revisions 看到差异 -
哦 - 嗯 - iOS 8 代码是否经过测试？我不认为 PHFetchResult.lastObject 返回 UIImage？
-
PHAsset 对象没有图像数据，它只有图像的“元数据”！
-
那个 fetchResult.lastObject 为你返回一个图像是很奇怪的。文档建议它应该返回一个 PHAsset，然后应该使用它来抓取图像并支持各种选项（大小、版本等）。我不知道这如何为您返回 UIImage 并为我返回 PHAsset。我添加了一个答案，其中包括适用于相关方的 PHAsset 方法 (@an0)
iBrad 的示例包括一个显然有效的 iOS8 sn-p，但我发现自己对他描述的返回类型感到困惑。这是一个抓取最后一张图像的 sn-p，包括版本和大小要求的选项。
值得注意的是能够请求特定版本（原始版本、当前版本）和大小。在我的情况下，由于我希望将返回的图像应用到按钮，我要求它调整大小并缩放以适合我应用它的按钮：
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
PHFetchResult *fetchResult = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions];
PHAsset *lastAsset = [fetchResult lastObject];
[[PHImageManager defaultManager] requestImageForAsset:lastAsset
targetSize:self.photoLibraryButton.bounds.size
contentMode:PHImageContentModeAspectFill
options:PHImageRequestOptionsVersionCurrent
resultHandler:^(UIImage *result, NSDictionary *info) {
dispatch_async(dispatch_get_main_queue(), ^{
[[self photoLibraryButton] setImage:result forState:UIControlStateNormal];
});
}];
【讨论】：
-
PHImageRequestOptions 是一个对象。您实际上可以传递一个枚举值“PHImageRequestOptionsVersionCurrent”吗？我想你想要的是： PHImageRequestOptions* options = [PHImageRequestOptions new]; options.version = PHImageRequestOptionsVersionCurrent;
基于 iBrad 的回答，这里有一个快速而肮脏的 Swift 版本，适用于 iOS 8.1：
let imgManager = PHImageManager.defaultManager()
var fetchOptions = PHFetchOptions()
fetchOptions.sortDescriptors = [NSSortDescriptor(key:"creationDate", ascending: true)]
if let fetchResult = PHAsset.fetchAssetsWithMediaType(PHAssetMediaType.Image, options: fetchOptions) {
imgManager.requestImageForAsset(fetchResult.lastObject as PHAsset, targetSize: self.destinationImageView.frame.size, contentMode: PHImageContentMode.AspectFill, options: nil, resultHandler: { (image, _) in
self.destinationImageView.image = image
})
}
注意：这需要 iOS 8.0+。请务必链接照片框架并在您的文件中添加“导入照片”。
【讨论】：
这是 iBrad 和 Javier 的答案的组合（效果很好），但我得到的是缩略图资产而不是全分辨率图像。其他一些人可能会觉得这很方便。
- (void)setCameraRollImage {
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
if ([group numberOfAssets] > 0) {
// Chooses the photo at the last index
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:([group numberOfAssets] - 1)] options:0 usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {
// The end of the enumeration is signaled by asset == nil.
if (alAsset) {
UIImage *latestPhoto = [UIImage imageWithCGImage:[alAsset thumbnail]];
[self.cameraRollButton setImage:latestPhoto forState:UIControlStateNormal];
}
}];
}
} failureBlock: ^(NSError *error) {
}];
}
【讨论】：
这是一种非常酷的方法，但其中一个问题是您必须能够在运行时实例化 PHPhotoLibrary 和其他 PHPhoto 类，否则在 iOS 7.XX 上会出现链接错误。只是想指出这一点，因为我现在遇到了这些问题。
此外，我认为您必须弱化照片框架中的链接，才能使应用在安装了 iOS 8.XX 和 iOS 7.XX 的两台设备上运行（尽管我尚未对此进行测试。）
我遇到的一个问题是如何在运行时实例化 PHPhotoLibrary。有没有人有代码sn-ps？
实际上，对于我正在开发的应用程序，我最终必须编写运行时代码来实例化 PHPhotoLibrary 类并调用 PHOTOS 框架方法，以便该应用程序可以在 iOS 7.x.x 和 iOS 8.x.x 上运行。其他人可能会遇到同样的问题，所以我提供了下面的代码 ->
// PHPhotoLibrary_class will only be non-nil on iOS 8.x.x
Class PHPhotoLibrary_class = NSClassFromString(@"PHPhotoLibrary");
if (PHPhotoLibrary_class) {
/**
*
iOS 8..x. . code that has to be called dynamically at runtime and will not link on iOS 7.x.x ...
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
[PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title];
} completionHandler:^(BOOL success, NSError *error) {
if (!success) {
NSLog(@"Error creating album: %@", error);
}
}];
*/
// dynamic runtime code for code chunk listed above
id sharedPhotoLibrary = [PHPhotoLibrary_class performSelector:NSSelectorFromString(@"sharedPhotoLibrary")];
SEL performChanges = NSSelectorFromString(@"performChanges:completionHandler:");
NSMethodSignature *methodSig = [sharedPhotoLibrary methodSignatureForSelector:performChanges];
NSInvocation* inv = [NSInvocation invocationWithMethodSignature:methodSig];
[inv setTarget:sharedPhotoLibrary];
[inv setSelector:performChanges];
void(^firstBlock)() = ^void() {
Class PHAssetCollectionChangeRequest_class = NSClassFromString(@"PHAssetCollectionChangeRequest");
SEL creationRequestForAssetCollectionWithTitle = NSSelectorFromString(@"creationRequestForAssetCollectionWithTitle:");
[PHAssetCollectionChangeRequest_class performSelector:creationRequestForAssetCollectionWithTitle withObject:albumName];
};
void (^secondBlock)(BOOL success, NSError *error) = ^void(BOOL success, NSError *error) {
if (success) {
[assetsLib enumerateGroupsWithTypes:ALAssetsGroupAlbum usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
if (group) {
NSString *name = [group valueForProperty:ALAssetsGroupPropertyName];
if ([albumName isEqualToString:name]) {
groupFound = true;
handler(group, nil);
}
}
} failureBlock:^(NSError *error) {
handler(nil, error);
}];
}
if (error) {
NSLog(@"Error creating album: %@", error);
handler(nil, error);
}
};
// Set the first and second blocks.
[inv setArgument:&firstBlock atIndex:2];
[inv setArgument:&secondBlock atIndex:3];
[inv invoke];
}
else {
// code that always creates an album on iOS 7.x.x but fails
// in certain situations such as if album has been deleted
// previously on iOS 8...x. .
[assetsLib addAssetsGroupAlbumWithName:albumName
resultBlock:^(ALAssetsGroup *group) {
handler(group, nil);
} failureBlock:^(NSError *error) {
NSLog( @"Failed to create album: %@", albumName);
handler(nil, error);
}];
}
【讨论】：
accepted answer (how to get last image) 的 Xamarin.iOS 版本，包括来自其他答案的所有通知：
private void ChooseLastTakenPictureImplementation()
{
var library = new ALAssetsLibrary();
// Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.
library.Enumerate(ALAssetsGroupType.SavedPhotos, (ALAssetsGroup assetsGroup, ref bool stop) =>
{
if (stop || assetsGroup == null)
{
return;
}
//Xamarin does not support ref parameters in nested lamba expressions
var lambdaStop = false;
//Check that the group has more than one picture
if (assetsGroup.Count > 0)
{
// Within the group enumeration block, filter to enumerate just photos.
assetsGroup.SetAssetsFilter(ALAssetsFilter.AllPhotos);
// Chooses the photo at the last index
assetsGroup.Enumerate(NSEnumerationOptions.Reverse, (ALAsset result, int index, ref bool innerStop) =>
{
// The end of the enumeration is signaled by asset == nil.
if (result != null)
{
var representation = result.DefaultRepresentation;
var latestPhoto = new UIImage(representation.GetImage(), representation.Scale, (UIImageOrientation)representation.Orientation);
// Stop the enumerations
lambdaStop = innerStop = true;
// Do something interesting with the AV asset.
HandleImageAutoPick(latestPhoto);
}
});
stop = lambdaStop;
return;
}
else
{
//Handle this special case where user has no pictures
}
}, error =>
{
// Typically you should handle an error more gracefully than this.
Debug.WriteLine(error.Description);
});
}
【讨论】：
感谢您的回答 iBrad 应用程序。
只是想指出当用户在他/她的照片卷上没有图像时的特殊情况的错误预防（我知道奇怪的情况）：
// Within the group enumeration block, filter to enumerate just photos.
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
//Check that the group has more than one picture
if ([group numberOfAssets] > 0) {
// Chooses the photo at the last index
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:([group numberOfAssets] - 1)] options:0 usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {
// The end of the enumeration is signaled by asset == nil.
if (alAsset) {
ALAssetRepresentation *representation = [alAsset defaultRepresentation];
UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullScreenImage]];
[self.libraryButton setImage:latestPhoto forState:UIControlStateNormal];
}
}];
}
else {
//Handle this special case
}
【讨论】：
参考 Liam 的回答。 fullScreenImage 将返回适合您设备屏幕尺寸的缩放图像。获取实际图像大小：
ALAssetRepresentation *representation = [alAsset defaultRepresentation];
ALAssetOrientation orientation = [representation orientation];
UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullResolutionImage] scale:[representation scale] orientation:(UIImageOrientation)orientation];
在fullResolutionImage 上引用 Apple 的 ALAssetRepresentation 类参考：
要从 CGImage 创建正确旋转的 UIImage 对象，请使用 imageWithCGImage:scale:orientation: 或 initWithCGImage:scale:orientation:, 传递方向的值 和规模。
【讨论】：
-
好点，虽然我只想要屏幕大小的图像。我相信这会对其他人有所帮助...谢谢！
我发现了一个错字，我不好意思承认的时间超过了它应该弄清楚的时间。也许它会为别人节省一些时间。
此行在indexSetWithIndex 之后缺少一个冒号：
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:[group numberOfAssets] - 1]options:0 usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {
【讨论】：
来自 iBrad 的出色回答，对我来说几乎是完美的。例外情况是它以原始方向返回图像（例如倒置、-90° 等）。
为了解决这个问题，我只是将fullResolutionImage 更改为fullScreenImage。
这里：
UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullScreenImage]];
现在是一种享受。
【讨论】：
-
感谢您的建议，我对您的回答投了赞成票，并将其纳入我的回答中！ :)
-
Liam 的建议做得很好，很高兴为 Stack 的世界做出贡献！
-
如果您只是显示图像，但实际上并没有获得全分辨率图像，则此方法有效，只是适合在用户设备上显示的图像。如果您需要完整尺寸的图片，您可以使用
UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullResolutionImage] scale:[representation scale] orientation:[representation orientation]]; -
@NateCook 这样做会给我一个警告：“从枚举类型'ALAssetOrientation'（又名'enum ALAssetOrientation'）到不同枚举类型'UIImageOrientation'（又名'enum UIImag ...'）的隐式转换”。执行此处描述的操作可能会更好：biasedbit.com/alasset-image-orientation
-
没关系 - 这基本上是 jemeshu 下面的答案。