New format and decoder (PDF) works as expected in core ImageSharp, but not in ImageSharp.Web

[skttl]

I've created a pdf format (and decoder) based on PdfLibCore, which I was going to use to be able to do thumbnails of pdf files. I've pushed the code to https://github.com/skttl/ImageSharpCommunity.Format.Pdf, and I intent to publish it to use for free on Nuget, when I get it working.

It works, when used just with ImageSharp, eg. in my TestApp console app, it opens up the pdf file, resizes to 100x100 and saves it as a png.

However, when I try to add it to a web app using ImageSharp.Web it fails. If I set breakpoints in PdfFormatDetector, I can see that it gets into this twice. First before actually doing anything in Decode, and then after loading the image as bitmap.AsBmpStream() in https://github.com/skttl/ImageSharpCommunity.Format.Pdf/blob/main/ImageSharpCommunity.Format.Pdf/PdfDecoder.cs#L36.

The end result is a 500 error page with this error:

SixLabors.ImageSharp.UnknownImageFormatException: Image cannot be loaded. Available decoders:
 - TIFF : TiffDecoder
 - BMP : BmpDecoder
 - TGA : TgaDecoder
 - GIF : GifDecoder
 - QOI : QoiDecoder
 - PBM : PbmDecoder
 - PNG : PngDecoder
 - JPEG : JpegDecoder
 - Webp : WebpDecoder
 - PDF : PdfDecoder

   at SixLabors.ImageSharp.Formats.ImageFormatManager.ThrowInvalidDecoder(ImageFormatManager manager)
   at SixLabors.ImageSharp.Formats.ImageFormatManager.GetEncoder(IImageFormat format)
   at SixLabors.ImageSharp.Web.FormattedImage..ctor(Image image, IImageFormat format, Boolean keepOpen)
   at SixLabors.ImageSharp.Web.FormattedImage.LoadAsync(DecoderOptions options, Stream source)
   at SixLabors.ImageSharp.Web.Middleware.ImageSharpMiddleware.ProcessRequestAsync(ImageCommandContext imageCommandContext, IImageResolver sourceImageResolver, ImageContext imageContext, Boolean retry)
   at SixLabors.ImageSharp.Web.Middleware.ImageSharpMiddleware.ProcessRequestAsync(ImageCommandContext imageCommandContext, IImageResolver sourceImageResolver, ImageContext imageContext, Boolean retry)
   at SixLabors.ImageSharp.Web.Middleware.ImageSharpMiddleware.Invoke(HttpContext httpContext, Boolean retry)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

Anyone know what I'm doing wrong here? Feels like ImageSharp.Web does more than ImageSharp does.

[skttl]

I found it! I needed to add an encoder too :)

[JimBobSquarePants]

Glad you figured it out. I've starred your repo. I want to see how this works!