PS hinting and overshoot

Ofir Shavit
Ofir Shavit Posts: 397
in Technique and Theory

At 24 and 28px in a PC browser the overshooted characters over overshoot.
Shoul I manually fix the autohint to the cap/x height, or overshoot less, or?


Comments

  • Grzegorz Luk (gluk)
    Grzegorz Luk (gluk) Posts: 161
    edited February 8
    You should probably take a look at the Chapter 5 in Adobe T1 font format
    and check BlueValues, BlueScale, BlueShift and BlueFuzz values in Private Dictionary.
     - BlueScale controls the point size at which overshoot suppression cease.
     - BlueShift is an distance beyond the flat position of alignment zones at which overshoot occurs.
  • Ofir Shavit
    Ofir Shavit Posts: 397
    edited February 8
    Thanks @Grzegorz Luk (gluk)
    Seems like I've overshooted too much.
  • Thomas Phinney
    Thomas Phinney Posts: 2,889
    It is hard to judge which of those two things seems true without looking at high-res outlines of overshooting letters in context with flat letters.

    But yes, if you are doing OpenType CFF (.otf), BlueScale and BlueShift are important. Glyphs and FontLab online help/tutorials both have extensive info about how to set these values in their app, and the effects of them.
  • Ofir Shavit
    Ofir Shavit Posts: 397
    I've tried testing the BlueScale values and it didn't have a significant impact, I'm happy that decreasing overshoot is saving me of dealing with that.
    I was interested to know if adjusting the zones is something to do at all? Because I've tried it once and it did help, but it complicates the workflow.

    CFF is quite a mystery to me quite from the start.
    I remmember back in the days, I've uploaded one of my first fonts here and @Mark Simonson said something like "it's CFF flavored..." and i'm like, is it?!

    I work with FL6 (for the fine tunning and production stages. For the first design and styling stages I still use Fontark) and I have no idea how to define my fonts to be CFF or not, and if it's even possible.

  • Thomas Phinney
    Thomas Phinney Posts: 2,889
    I am going to simplify slightly:

    .otf is generally OpenType CFF
    .ttf is always TrueType

    The dividing line between OpenType with TrueType outlines and old TrueType is mostly imaginary, unless one happens to use things that were not in the old TrueType specs.

    It is technically legal to give an OpenType TrueType font a .otf extension, and it will work in just about all environments of the last 20 years, but typically nobody does this because… why confuse people? And why make it NOT work some ancient places it would have otherwise, if you had only given it a .ttf extension?
  • Ofir Shavit
    Ofir Shavit Posts: 397
    edited February 8
    Lets simplify it more...
    So PS .otf is CFF.

    It's possible to create OT-TT as .otf , thus make it not CFF. But it's not PS.

    Why not just say PS .otf, and relate to the CFF tables?
  • Florian Pircher
    Florian Pircher Posts: 176
    When talking about OpenType (OT) fonts, there are TrueType-based fonts (TT) and CFF-based fonts. CFF in turn is based on tech from PostScript (PS).

    By convention, OT-CFF font files use the file extension .otf while OT-TT files use .ttf. For most software, the file name extension is irrelevant as the CFF/TT distinction is made based on the contents of the font file, not the file name.
  • Ofir Shavit
    Ofir Shavit Posts: 397
    Both TT and PS are OpenType these days, so I take OT as trivial (while remmembering that there's also an old TrueType format)
    So it's about the relation between PS and CFF, which I understand as completely related.

    The difference between TT and PS is quite understandable, and if there's no PS without CFF, so I see it as a feature of PS not the opposite.
    At least at the moment  :/  
  • Christopher Slye
    Christopher Slye Posts: 152
    If it helps, consider this description on Wikipedia:

    Compact Font Format (also known as CFF font format, Type 2 font format, or CFF/Type 2 font format) is a lossless compaction of the Type 1 format using Type 2 charstrings.

    And if you really want to get into it, you can read the CFF specification.
  • Ofir Shavit
    Ofir Shavit Posts: 397
    Yes, I get the picture. Thanks!
  • John Hudson
    John Hudson Posts: 3,204
    CFF is a compression format for outline data that could also be encoded as Type 1 data, which was a font-specific subset of the PostScript layout language, But my understanding from Adobe engineers is that Type 2 compression means that there is zero actual PostScript code in CFF. So the whole notion of ‘PostScript’ or ‘PS’ flavour OpenType is really a misnomer. It was a convenience in explaining the two flavours of OpenType when the format was first introduced, because both font makers and customers were familiar with the concept of PS fonts, but it is not good terminology to use in technical discussions.

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