Swift PHImageManager图片库图像选择了收集视图单元格后获取PHImageManagerMaximumSize

Question

My scenario, I am loading photo gallery photos into horizontal collection view cell Imageview. For quick image loading purpose I gave PHImagemanager targetSize: CGSize(width: 120.0, height: 120.0) . Now once user sleeted cell in horizontal CollectionView need to get PHImageManagerMaximumSize actual high quality photo for preview Image. How to achieve it?

cell.tag = Int(manager.requestImage(for: asset,
                                            targetSize: CGSize(width: 120.0, height: 120.0),  //PHImageManagerMaximumSize
                                            contentMode: .aspectFill,
                                            options: option) { (result, _) in
                                            cell.picImage?.image = result

})

// MARK: - UICollectionViewDelegate protocol
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        let selectedCell = collectionView.cellForItem(at: indexPath) as! GalleryCollectionViewCell
        previewImage.image = selectedCell.picImage.image // here I need to get full size exact image (not cropped image)
}

Answer 1

You should save 2 image. First is full original image, second is cropped image.

Firstly: When user select image, save original image to disk ( crop image with protect aspect ratio and careful for image size ) and the same image crop again ( 120x120 ) and save disk too.

And read from disk to memory when cell visible.

Be careful! If images too huge, your memory usage increase too much and OS will be crash your app so don't keep too much images in your memory

You can set buffer images for visible cell count.

And that if user select cell, you can show original image