Trying to generate text in a blazor webassembly context, failing to load fonts

[MaddoScientisto]

I'm trying to use imagesharp in a blazor webassembly application, I tried to load a provided ttf font (I don't know if there's any other way to do it) but when I try to add it to a FontCollection I just get the following error:

Invalid value for 'classFormat' 0. Should be '1' or '2'.
SixLabors.Fonts.InvalidFontFileException: Invalid value for 'classFormat' 0. Should be '1' or '2'.
   at SixLabors.Fonts.Tables.AdvancedTypographic.ClassDefinitionTable.Load(BigEndianBinaryReader reader, Int64 offset)
   at SixLabors.Fonts.Tables.AdvancedTypographic.GlyphDefinitionTable.Load(BigEndianBinaryReader reader)
   at SixLabors.Fonts.Tables.AdvancedTypographic.GlyphDefinitionTable.Load(FontReader reader)
   at SixLabors.Fonts.Tables.TableLoader.Load[GlyphDefinitionTable](FontReader reader)
   at SixLabors.Fonts.FontReader.TryGetTable[GlyphDefinitionTable]()
   at SixLabors.Fonts.StreamFontMetrics.LoadFont(FontReader reader)
   at SixLabors.Fonts.StreamFontMetrics.LoadFont(Stream stream)
   at SixLabors.Fonts.FontCollection.AddImpl(Stream stream, CultureInfo culture, FontDescription& description)
   at SixLabors.Fonts.FontCollection.Add(Stream stream, FontDescription& description)
   at SixLabors.Fonts.FontCollection.Add(Stream stream)
   at ImageSharpFontExample.Pages.Index.MakeImage()
   at ImageSharpFontExample.Pages.Index.IncrementCount()
   at Microsoft.AspNetCore.Components.ComponentBase.CallStateHasChangedOnAsyncCompletion(Task task)
   at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask(Task taskToHandle, ComponentState owningComponentState)

I made a small project with the code I used here:
https://github.com/MaddoScientisto/ImageSharpFontExample/blob/2db7d557cd595996afda48812ca1ac23c78b8c89/ImageSharpFontExample/Pages/Index.razor

Am I doing this completely wrong? I just want to draw text to an image (among other things), what is the proper way if this isn't it?
I don't really care about any specific font, as long as something works in the end.

[tocsoft]

That error would generally imply its an unsupported font file version that has features our library doesn't know how to process.

If you could try using one of the fonts from our test suite (I would suggest OpenSans), That would help verify if its an issue with the version of the the version font your using or the library when ran from webassembly.

FYI Nothing in your code jumping out as fundamentally wrong... I do feel it prudent to warn you however that we can't promise you will find ImageSharp will be particularly performant when run in webassembly (.net is missing a lot of the optimisation we rely on when run in the browser)

[MaddoScientisto]

Thank you, that worked great, I just got that font from some random site so that has to be why. I updated the sample for posterity.

For what I have to do performance seems to be decent enough, I just need to generate downloadable images, it's fine if it takes a few seconds.

Does AddSystemFonts do anything at all on webassambly?

[tocsoft]

we have no special logic for webassembly.

add system fonts/SystemFontsCollection literally just loads *.ttf file from well-know folders locations so I would expect it to fail with a PlatformNotSupportedException (but I'm not sure that the behaviour is for System.IO.File/System.IO.Directory on webassembly)

[JimBobSquarePants]

@MaddoScientisto is the Arial.ttf font in your sample the one that was failing?

Class Definition tables support only 2 formats https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#class-definition-table-format-1 so I’m curious to see if there’s something else causing us to read the font incorrectly