How to Create thumbnail from local files - swift

Question

I want to create a thumbnail image for files (word, excel, video ....)
This what i did:
import QuickLook
class ThumbsCreator: NSObject {
private var file : File?
init(file: File?) {
super.init()
self.file = file
}
func createThumb() {
let url = URL(string: (self.file?.path()))
}
}

Answer 1

After a lot of search, I found this solution :
import PDFKit
import AVKit
import WebKit
func createThumb() {
let url = URL(string: (self.file?.path()))
switch file?.type {
case: FileType.image.rawValue:
let image = UIImage(contentsOfFile: (url?.path)!)
_finalImage = self.createScaledImage(image: image!)
break
case: FileType.office.rawValue:
//Loading.......
break
case FileType.Pdf.rawValue:
guard let doc = PDFDocument(url: url!) else {return}
guard let page = doc.page(at: 0) else {return}
_finalImage = page.thumbnail(of: CGSize(width: 768, height: 1024), for: .cropBox)
break
case: FileType.video.rawValue:
let asset = AVAsset(url: url!)
let imageGenerator = AVAssetImageGenerator(asset: asset)
imageGenerator.appliesPreferredTrackTransform = true
let time = CMTime(seconds: 2, preferredTimescale: 1)
do {
let imageRef = try imageGenerator.copyCGImage(at: time, actualTime: nil)
_finalImage = UIImage(cgImage: imageRef)
} catch let error{
print("Error: \(error)")
}
break
}
}
func createScaledImage(image: UIImage) {
let THUMB_WIDTH = 150.0 - 40.0
let THUMB_HEIGHT = THUMB_WIDTH - 23.0
var itemThumb = resizeImage(image: image, constraintSize: CGSize(width: THUMB_WIDTH, height: THUMB_HEIGHT))
let thumbRect = CGRect(x: 0, y: 0, width: 10, height: 10)
UIGraphicsBeginImageContextWithOptions(thumbRect.size, true, 0.0)
let context = UIGraphicsGetCurrentContext()
// Fill a white rect
context?.setFillColor(gray: 1.0, alpha: 1.0)
context?.fill(thumbRect)
// Stroke a gray rect
let comps : [CGFloat] = [0.8, 0.8, 0.8, 1]
let colorSpace = CGColorSpaceCreateDeviceRGB()
let strokeColor = CGColor(colorSpace: colorSpace, components: comps)
context?.setStrokeColor(strokeColor!)
UIRectFrame(thumbRect)
//CGColorRelease(strokeColor!)
itemThumb.draw(in: thumbRect.insetBy(dx: 1, dy: 1))
itemThumb = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
self.finishThumCreation(image: image)
}
}

Answer 2

Starting from iOS 13 and macOS 10.15, there is the QuickLook Thumbnailing API. It supports any file format for which the OS can provide a preview: either because the OS knows this format or because the owner of the third-party format provided a QuickLook plugin.
Here is an example based on Apple's tutorial:
func thumbnail(for fileURL: URL, size: CGSize, scale: CGFloat) {
let request = QLThumbnailGenerator
.Request(fileAt: fileURL, size: size, scale: scale,
representationTypes: .lowQualityThumbnail)
QLThumbnailGenerator.shared.generateRepresentations(for: request)
{ (thumbnail, type, error) in
DispatchQueue.main.async {
if thumbnail == nil || error != nil {
// Handle the error case gracefully.
} else {
// Display the thumbnail that you created.
}
}
}
}
On macOS before 10.15, in my app I fallback to NSWorkspace.shared.icon(forFile:) which provides a document icon based on the file type (but not a thumbnail).

Answer 3

You can use https://developer.apple.com/documentation/uikit/uidocumentinteractioncontroller/1616801-icons
var icons: [UIImage] { get }
let controller = UIDocumentInteractionController(url:someUrl)
print(controller.icons.first)
Only for a video
extension UIViewController {
func thumbnail(_ sourceURL:URL) -> UIImage {
let asset = AVAsset(url: sourceURL)
let imageGenerator = AVAssetImageGenerator(asset: asset)
imageGenerator.appliesPreferredTrackTransform = true
let time = CMTime(seconds: 1, preferredTimescale: 1)
do {
let imageRef = try imageGenerator.copyCGImage(at: time, actualTime: nil)
return UIImage(cgImage: imageRef)
} catch {
print(error)
return UIImage(named: "NoVideos")!
}
}
}

Answer 4

There's no good API for this yet. There is NSURLThumbnailDictionaryKey, but YMMV. You can indeed get icons via UIDocumentInteractionController.