OTF & TTF font files

[Michael Rowley]

I came across this statement a liitle while ago:

'Fonts containing TrueType outlines may have either .OTF or .TTF, depending on the desire for backward compatibility on older systems or with previous versions of the font.'

Has anyone ever come across an OTF file containing TrueType outlines, and if so, who was the maker?

[iamback]

Originally Posted by Michael Rowley

Has anyone ever come across an OTF file containing TrueType outlines, and if so, who was the maker?

How would I tell if a file (with an .otf extension) has TrueType outlines? I can't answer the question if I don't know what to look for.

[ktinkel]

Originally Posted by iamback

How would I tell if a file (with an .otf extension) has TrueType outlines?

By definition, .OTF fonts contain PostScript Type 1 outlines. The OT fonts with .TTF have TrueType outlines.

[Michael Rowley]

Originally Posted by ktinkel

By definition, .OTF fonts contain PostScript Type 1 outlines. The OT fonts with .TTF have TrueType outlines.

Not according to the Microsoft document from which I just quoted. All Adobe OTF files have PS outlines (and all files supplied by Microsoft have TTF extensions and outlines), but that doesn't necessarily apply to every maker.

[Michael Rowley]

Originally Posted by iamback

How would I tell if a file (with an .otf extension) has TrueType outlines? I can't answer the question if I don't know what to look for.

You (possibly) and I (certainly) wouldn't know if a font file with the extension OTF had TrueType or PS outlines, partly because both of us use Windows NT5, which doesn't care; probably many are in the same position, but there are some experts on fonts here. If you're not an expert, you'll rely on the maker's information, which is how I 'know' that all Adobe font files with OTF extensions have PS outlines.

[iamback]

Originally Posted by Michael Rowley

You (possibly) and I (certainly) wouldn't know if a font file with the extension OTF had TrueType or PS outlines, partly because both of us use Windows NT5, which doesn't care

But a hex viewer doesn't care about NT5. I was thinking there must be some sort of signature that enables one (or software) to tell them apart since an extension is essentially meaningless anyway.

[Michael Rowley]

Originally Posted by iamback

But a hex viewer doesn't care about NT5. I was thinking there must be some sort of signature that enables one (or software) to tell them apart since an extension is essentially meaningless anyway.

Yes, of course there is, but you will have to go to the Open Type Specification for that.

Since the specification is the joint work of Adobe and Microsoft, the statement by M. that an OTF file may contain TrueType outlines could be true, but never implemented by anybody; or it could have been M.'s intention to use the OTF extension for its OT files, but thought better of it.

[iamback]

Originally Posted by Michael Rowley

Yes, of course there is, but you will have to go to the Open Type Specification for that.

Found it (links in my reply to KT). The Organization of an OpenType Font section says:

OpenType fonts that contain TrueType outlines should use the value of 1.0 for the sfnt version. OpenType fonts containing CFF data should use the tag 'OTTO' as the sfnt version number.

NOTE: The Apple specification for TrueType fonts allows for 'true' and 'typ1' for sfnt version. These version tags should not be used for fonts which contain OpenType tables.

So... if I go looking first for files with an .OTF extension, and within that set for files which contain the string 'OTTO' then whatever is is not matched by the sub-search must be files with TrueType outlines (given I do not have Mac fonts - at least no working ones!). No hex viewer needed even, just plain Search can do that.

Result on my machine: 17 files with an ".otf" extension (lower case), 13 of which originating from Adobe; all 17 contain the string "OTTO".

Looking with a hex viewer at one of them, the string "OTTO" is right at the start of the file, so finding that (or another sfnt version) is simply a matter of looking at the first 4 bytes (provided the file contains only one font - but if it has multiple fonts it should have a TTC extension, not OTF).

[ktinkel]

Originally Posted by iamback

So... if I go looking first for files with an .OTF extension, and within that set for files which contain the string 'OTTO' then whatever is is not matched by the sub-search must be files with TrueType outlines (given I do not have Mac fonts - at least no working ones!).

Sure you do — OT fonts work on either platform. One of the rationales for OT fonts was that platform versions would no longer be required.

[iamback]

Originally Posted by ktinkel

Sure you do — OT fonts work on either platform. One of the rationales for OT fonts was that platform versions would no longer be required.

Yes, they should - I'm merely saying that I don't have working ones (that I got as a Mac file), and I don't know why they don't work either. No problem, it was just an observation.