OT tables dropped in OTF to TTF conversion

[Mark Simonson]

When I convert from .otf to .ttf, the GPOS and GSUB tables in the source font are not carried over to the destination font. I checked the various preferences and tried different settings, but I can't get TT Pro to retain the OT tables no matter what I try.

I thought it might be something about the way I generated my OTF fonts, but I tried OTFs from other sources and have the same results.

Since there is an option to delete them in the "OpenType Layout Options" panel, that would seem to imply that the expected behavior is that they will be carried over. Is there any way to get it to include OT tables, or is this a bug, or what?

I'm using TT Pro 3.02 on MacOS 10.6.4.

[Ray Larabie]

I've never been able to get the table to survive OTF-TTF conversion. Over the years, I've found that TT Pro can only be used for really basic conversions.

Kerning classes not only don't survive conversion but they don(t even can expanded to a flat table. All those kerns get thrown away. I don't know about you, but I set up period as a comma and basequotes parent and a straight quote as a parent for all other quotes. When I convert with TTPro, it really ruins the kerning for all my fonts. The real question is: what is TTPro actually good for?

[Mark Simonson]

Well, I figured out a workaround right away, but I was hoping I was missing something, and it wouldn't be needed.

Anyway, the workaround is this:
- ttx both the original OTF and the converted TTF
- Open the ttx'd OTF in a text editor and copy the GSUB and GPOS tables
- Open the ttx'd TTF and paste in the two tables
- ttx the ttx'd TTF to revert it back to TTF format (tables now restored)

It works, but it'd be better if TT Pro did the right thing to begin with.

[Arno Enslin]

@ Mark

Why so complicate? You can decompile tables only and merge them into other font files with TTX. There is no need to paste and copy anything.

[Mark Simonson]

Sure, of course, I just forgot. The point was, it's possible to restore the tables using ttx (several ways, some less complicated than others) as a workaround. I just don't understand why a workaround is necessary at all. TT Pro should do the right thing in the first place. That would be even less complicated.

[Arno Enslin]

Sure, of course, I just forgot. The point was, it's possible to restore the tables using ttx (several ways, some less complicated than others) as a workaround. I just don't understand why a workaround is necessary at all. TT Pro should do the right thing in the first place. That would be even less complicated.

That’s true, Mark. (I once tried TransType and found it so uncomfortable and useless, that I thought: Not FontLab, but the user should be paid for the program.)

[Ray Larabie]

TransType pro was disappointing for me because it couldn't even do basic conversion with it. Converting a TrueType Windows family to Mac Postscript: wouldn't that be nice? But it was such a struggle to get it to work. It took hours to convert a font family, mostly through trial an error. Converting from a vfb would simply crash. Not very useful. OTF to Mac Postscript rarely resulted in a working font, plus I'd have to go into Fontlab and expand the class based kerning myself. Despite the quality loss from converting from Postscript curves (OTF), to TrueType curves (TTF) then back to Postscript curves, it was the only way I could convert. Lucky for me, I've discontinued Mac Postscript fonts. But it was a constant struggle every time I used TransType Pro. Maybe it's useful for converting Mac PS fonts to Win TTF, I don't know. Lesson learned.

[Arno Enslin]

@ Ray

If there is a way, to emulate Windows on an old MAC, you could give Crossfont a try. Crossfont cannot convert from TT to PS or the other way around, but from MAC to PC and PC to MAC only. I think, the conversion of the curves from TT to PS is lossless, as far as you don’t change the UPM. In other words: If you have converted the font one time from PS to TT, you can repeat the conversion as often, as you want. You have a loss in the first conversion only. So it may be, that it is useful, to design in TT but not in PS modus, if you plan to release both flavors. (You loose the hinting in every conversion of the outline flavors.)

One of the main problems with TransType is, that you cannot save VFB files. If you discover a problem, you have to repeat the process. TransType is pure trash, not only because of the bug with the OT tables, but it simply is not user friendly.

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