CODEWITHSUNDEEP
iosswiftxcodefoundationquicklook
T. Pasichnyk
T. Pasichnyk

Reputation: 732

QLThumbnailGenerator saveBestRepresentation wrong content type Swift iOS 13+

When completing a task I have stumbled upon an iOS 13+ API that can solve my problem - https://developer.apple.com/documentation/quicklookthumbnailing/creating_quick_look_thumbnails_to_preview_files_in_your_app

It works as intended, but to complete my task I need to save created thumbnail to a disk, which I am trying to do using - https://developer.apple.com/documentation/quicklookthumbnailing/qlthumbnailgenerator/3237298-savebestrepresentation

func saveBestRepresentation(for request: QLThumbnailGenerator.Request, 
                         to fileURL: URL, 
                contentType: String, 
                 completion completionHandler: @escaping (Error?) -> Void)

Here is my code:

/// Uses quick look to asynchronously create best possible thumbnail image at path
static func createThumbnailFor(_ inputUrl: URL, at outputUrl: URL) {
    let size: CGSize = CGSize(width: 60, height: 90)
    let scale = UIScreen.main.scale

// Create the thumbnail request.
let request =
    QLThumbnailGenerator.Request(
        fileAt: inputUrl,
        size: size,
        scale: scale,
        representationTypes: .all)

// Retrieve the singleton instance of the thumbnail generator and generate the thumbnails.
let generator = QLThumbnailGenerator.shared
generator.saveBestRepresentation(for: request, to: outputUrl, contentType: "image/jpg") { (error) in
    if let error = error {
        print(error.localizedDescription)
    }
}

}

I am receiving the following error:

2020-07-28 13:08:01.259835+0300 SomeAppName[4748:1236635] *** Terminating app due to uncaught exception 'QLThumbnailGeneratorInvalidContentType', reason: 'image/jpg is not a supported image type'

I have tried many different types and looked through the headers but it only says that 'The content type of the thumbnail image that you want to save. Use a type that is supported by CGImageDestination, such as kUTTypePNG or kUTTypeJPEG.'. Unfortunately kUTTypePNG and kUTTypeJPEG are both deprecated. What content type should work in this case?

Upvotes: 0

Views: 978

Answers (3)

matt
matt

Reputation: 535954

The iOS 14 way:

At the top of the file, import UniformTypeIdentifiers. Now change

contentType: "image/jpg"

to

contentType: UTType.jpeg.identifier

Upvotes: 1

Mustang
Mustang

Reputation: 417

MIME types (e.g. "image/jpg") and UTIs (e.g. "public.jpeg") are two different things. Apple APIs take UTIs, generally, including the one you are trying to use. Symbols like kUTTypeJPEG are just names for constant strings. You can use a string literal instead of the symbolic name if you wish.

Some common examples:

"public.jpeg"  (kUTTypeJPEG)
"public.png"  (kUTTypePNG)
"com.compuserve.gif" (kUTTypeGIF)
"public.tiff"  (kUTTypeTIFF)
"public.heic"  (no symbolic name defined)

For fun, how about "com.microsoft.bmp" (kUTTypeBMP)

If you know the MIME type, you can get the UTI like so:

uti = UTTypeCreatePreferredIdentifierForTag( kUTTagClassMIMEType, mimeType, (CFStringRef)0);

If you know the UTI, you can get the MIME type like so:

mimeType = UTTypeCopyPreferredTagWithClass( uti, kUTTagClassMIMEType);

If you want the list of UTIs you can use in your case you can:

CFArrayRef utis = CGImageDestinationCopyTypeIdentifiers();

(These are all C snippets. Swift may be slightly different.)

Upvotes: 0

Kap
Kap

Reputation: 1

"public.png" works for me.

Upvotes: 0

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