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FAQ FontLab & TypeTool — Hinting

Q: What are all those hints? I have noticed that the one of the TT import options is to keep Save "TT hinting information." However when I import a hinted font the hint button on the option bar does not show any hints in the edit window. If I autohint the font and save it as TT, and I open it again I can't see the hints. If I save it as a *.VFB file the hints are their when I open it. It their something I am missing?

A: Yes. There are 3 kind of hints in FontLab: Type 1 hints (green lines in Edit window), TrueType visual instructions (seen in TrueType hinting tool only) and original, saved TrueType instructions that can't be seen. You can see what hints your characters have in Font window (small colored marks in character cells give information about present hints ? look into help for description)  and in right-top area of Glyph window.

Q: What pixels are "inside"? One problem I'm having in particular is that it is my understanding that when an outline is rasterised, the rule is that pixel centers which fall inside, or on the outline, are turned on whilst the others are turned off and the object of the instructions is to modify the outline such that the desired pixels are turned on. I've noticed on many occasions that after adding visual instructions, odd pixels lying outside the adjusted outline are still turned on. Can you explain this?

A: Yes. This may happen for two reasons:

1. Drop-out control. If stem (usually diagonal or rounded) is too thin, some pixels with centers outside outline will be turned on to prevent drop-outs.

2. Gray "hinted" outline that you can see when FL's TrueType hinting tool is active is generated by the FontLab according to FontLab's rules. Bitmap that previews pixels is generated by the Windows TrueType rasterizer. We decide to do this to be sure that our "understanding" of TrueType instructions is correctly rendered by the Windows TT rasterizer. Sometimes our outline is not precise. May be it's even good ? it's better to set hints that generate correct bitmap even in "edge" situations, when different decisions can be made by different rasterizers.

Q: Are there hinting tutorials available?

A: As usual, start with the FontLab user's manual. It explains hinting very extensively. For PostScript hinting, also read Hinting Type 1 Fonts by David Lemon. For TrueType hinting, read SIL Hinting Tutorial by Victor Gaultney. More links are available at MyFonts.

Q: What FontLab does with font-level TrueType hints? Do your current products preserve the font-level (TrueType) hinting?  (pre-program, control value table, font program) This is what would be necessary to import a super-hinted TT font, re-arrange glyphs, and preserve the total hinting.

Yes. Here is what it does:

1. If "Save TrueType hinting information" (in Import options) option is on, then it stores all hinting data: PREP, CVT, FPGM, HDMX and glyph programs.

2. If "Keep existing TrueType instructions" (in export options) switch is on, all hinting data is restored. Note that "touched" characters (any point is moved, inserted or deleted) lose glyph-level hinting data. Font-level hinting data remain until single character remain hinted. Also note that VDMX table is not stored in any way.

3. If any of characters have visual hints or autohinting option is on, then FontLab's font-level hints are added to original hints (if they need to be restored), or only FontLab font-level hints are exported. If font-level hinting data is added, then special commands are used in each character-level instruction to avoid interference between two sets of font-level hinting. This makes fonts bigger for some 1-2%, and in some cases decreases font performance for a bit. So, when you make TrueType hinting for most characters in your font, we recommend to not keep original hints.