从Photos.app获取最新图片？

Question

我已经看到其他应用程序可以从照片应用程序中导入最后一张照片以便快速使用,但据我所知,我只知道如何获取A图像而不是最后一张(最近的图像).谁能告诉我如何获取最后一张图片？

Answer 1

此代码段将从相机胶卷(iOS 7及更低版本)获取最新图像:

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及以上版本:

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];

                                           });
                                       }];

Answer 2

iBrad的答案很棒,对我来说几乎是完美的.唯一的例外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,我只是改变了fullResolutionImage到fullScreenImage.

这里:

UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullScreenImage]];

它现在有效.

Answer 3

iBrad的例子包括一个显然有效的iOS8片段,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个图像的片段,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,当前)和大小.在我的情况下,因为我希望将返回的图像应用于按钮,我请求它的大小和缩放以适合我正在应用它的按钮:

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];

                                           });
                                       }];

Answer 4

感谢您对iBrad Apps的回答.

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
    }

Answer 5

好吧,这是一个解决方案,如何从Swift 3家伙加载画廊的最后一个图像:

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)
            }
        })
    }

}

如果你需要更快的速度,你也可以使用PHImageRequestOptions和设置:

options.deliveryMode = .fastFormat
options.resizeMode = .fast

这是你在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)
      }
}

Answer 6

请参阅利亚姆的回答.fullScreenImage将返回适合您设备屏幕尺寸的缩放图像.要获得实际图像大小:

  ALAssetRepresentation *representation = [alAsset defaultRepresentation];
  ALAssetOrientation orientation = [representation orientation];
  UIImage *latestPhoto = [UIImage imageWithCGImage:[representation fullResolutionImage] scale:[representation scale] orientation:(UIImageOrientation)orientation];                    

引用Apple的ALAssetRepresentation类参考fullResolutionImage:

要从CGImage创建正确旋转的UIImage对象,可以使用imageWithCGImage:scale:orientation:或initWithCGImage:scale:orientation :,传递方向和比例的值.