Metafile (WMF / EMF) support

[manfromarce]

Is there any plan for metafile decoding support? While .wmf and .emf are rare as standalone files, they are still common as embedded images inside Office documents and RTF. I'm currently working on a project which converts between document formats and the lack of support for handling metafiles is the only thing which prevents replacing System.Drawing.Common with a cross-platform alternative completely. Magick.NET and SkiaSharp also don't support these on non-Windows platforms but they rely on native libraries, while I'm confident ImageSharp can accomplish this.

UPDATE: This library could be used as a starting point.

[JimBobSquarePants]

If that's something you'd be happy to make a start contributing ,I'd be happy to help out.

[manfromarce]

I would like to do this, the problem is that metafiles are made of records to be drawn, so ImageSharp.Drawing would be needed. Also WMF files aren't really device-independent and handling them is complex, I would start with EMF only.

[JimBobSquarePants]

That would be great! The decoders can be added to ImageSharp.Drawing then. I need to do some work to update the drawing library to work with the latest ImageShap v4 builds in main here though first.

Regarding WMF. It seems to me that if we passed a specific DPI value as decoder options that would allow us to implement the format decoder in a device independent manner?

[manfromarce]

Yes, the dimensions are expressed in twips (1/1440 inch) with a scale factor but there is no embedded DPI value.
So should the decoder have similar APIs to other formats but in the ImageSharp.Drawing package?

[JimBobSquarePants]

Yeah it would. I have a public abstract base class in main that would act as the foundation for your decoder. It's designed for passing custom decoding options.

I'm going to start looking at ImageSharp.Drawing to see if I can get it updated to support the new code.