Why not support 48bpp png images?

[e8-ShiWei]

https://github.com/mono/libgdiplus/blob/7d12c7d1e42669d3d92999094335ec30998e5976/src/pngcodec.c#L512

Image format is unknown. We got this error while processing png images.

I checked pngcodec.c and found this comment.

/* 24 and 32bpp are supported, 48, 64bpp aren't, see http://bugzilla.ximian.com/show_bug.cgi?id=80693 */

This URL can no longer be opened, we don’t know why it doesn’t support 48bpp. Could someone help us answer this question?

Thanks.