4. True­Type out­lines and TT hinting

Before pro­duc­ing a TrueType-hinted font in Font­Lab Stu­dio, you should ver­ify that you have the fol­low­ing ele­ments present in the font:

  • PS align­ment zones
  • PS stan­dard stems
  • PS hints (with replace­ment hints)

These three para­me­ters will be used by FLS to auto­mat­i­cally gen­er­ate high-level TT hinting.

4.1. TT hint­ing UI elements

Pref­er­ences

When a TrueType-flavored font is gen­er­ated (includ­ing the sit­u­a­tion when the ras­ter­ized pre­views are gen­er­ated in the TrueType Hinting mode), a num­ber of set­tings can be con­trolled in Preferences. In the Pref­er­ences sec­tion Generating OpenType & TrueType, the TrueType/OpenType TT (.ttf) page con­trols how TT hint­ing is writ­ten into the gen­er­ated font.

The options Write stored TrueType native hinting and Export visual TrueType hints should be enabled.

Note: if the Autohint unhinted glyphs option is enabled, then glyphs with no high-level TT hints are being auto­hinted in the back­ground so that in the TrueType Hinting mode, you won’t see any high-level TT hints but the pre­views will be hinted. If you want to use the True­Type Hint­ing mode to reli­ably pre­view the results of the TT auto­hint­ing, dis­able this option.

[sin­glepic w=645 id=13]

The TrueType Autohinting page includes sev­eral options that give you fine-grade con­trol in how PS hints are con­verted into high-level TT hints.

The most impor­tant set­ting here is per­haps Single link attachment precision. This numer­i­cal val­ues con­trols the tol­er­ance in which FLS will match each stem width with the TT stan­dard stems (CVT entries). For exam­ple, if one of the TT stan­dard stems is 168, and if the pre­ci­sion set­ting is set to 3, then all stems that are of widths 165171 will be linked to that value, but not stems that are 164 or 172 units wide.

Please refer to the FLS man­ual for more detailed expla­na­tion of those options.

[sin­glepic w=645 id=14]

Font Info

The Font Info sec­tion TrueType-specific settings / Font smoothing con­trols the ppem sizes at which low-level TT hint­ing and stan­dard Win­dows font smooth­ing should be turned on and off.

[sin­glepic w=645 id=15]

Appli­ca­tion windows

To view and mod­ify the high-level TT hint­ing, open any glyph in a Glyph Win­dow and choose Tools / Hints & Guides / TrueType Hinting.

[sin­glepic w=645 id=16]

The TrueType Hinting tool has numer­ous sub­pan­els that you can open: the TrueType Options panel, the TrueType Program panel and the TrueType Preview panel.

Note that the TrueType Preview panel uses the sys­tem ras­ter­izer to gen­er­ate the ras­ter­ized pre­views, so the pre­view results on Mac OS X and Win­dows will dif­fer. FLS for Win­dows allows you to select the ras­ter­i­za­tion mode used to gen­er­ate the pre­views (black-and-white, stan­dard Win­dows smooth­ing or ClearType). FLS for Mac OS X does not offer this functionality.

Also keep in mind that if the font con­tains stored low-level TT hints or the option Autohint unhinted glyphs is enabled in the Pref­er­ences, the pre­views gen­er­ated by the TrueType Preview panel will be auto­hinted even if no high-level TT hints are present.

Click­ing on the icon on the TrueType Options panel opens the TT Hinting Options dia­log that allows you to con­trol the TT stan­dard stems and the TT align­ment zones. After con­vert­ing PS hint­ing to TT hint­ing, the TT stems and zones cor­re­spond to the PS stan­dard stems and align­ment zones that have been defined in Font Info, but this can be modified.

[sin­glepic w=645 id=17]

[sin­glepic w=645 id=18]

4.2. Out­line con­ver­sion and TT autohinting

Note: these next steps mod­ify the actual out­lines of your glyphs, so please be sure you have saved a backup copy of your orig­i­nal design with Post­Script outlines.

Also, please keep in mind that when FLS con­verts PS out­lines into TT out­lines, the qual­ity of con­ver­sion depends on the UPM size of the font. The smaller the UPM size, the fewer TT out­line points FLS will pro­duce. If your UPM size is very high, the num­ber of TT out­line points will be large, which may result in less sat­is­fac­tory TT auto­hint­ing results (since FLS may become “con­fused” as to which out­line points would best be con­trolled by the TT hint­ing instruc­tions). It’s also pos­si­ble to reduce the num­ber of TT out­line points after out­line con­ver­sion, using the FLS Optimize fea­ture. As a rule: if pos­si­ble, try to keep the num­ber of TT out­line points at a rea­son­able minimum.

You should per­form the fol­low­ing steps to con­vert a PS-hinted font into a TT-hinted font with True­Type outlines:

  1. Go to Preferences / Generating OpenType & TrueType / TrueType Autohinting and fine-tune the way PS hint­ing is con­verted into TT hint­ing. In par­tic­u­lar, check the Single link attachment precision value.
  2. Close all opened glyph windows.
  3. Choose Tools / Action Set.
  4. From the Contour sec­tion, add the action Curves to TrueType.
  5. From the Contour sec­tion, add the action Contour direction.
  6. Click on the added Contour direction action in the Action set list and click on the option Set direction to TrueType.
  7. If you decided to reduce the num­ber of TT out­line points after the con­ver­sion (which may result in small adjust­ments of the glyph shapes), from the Contour sec­tion, add the action Optimize. Click on the added action and in the action’s options, set Auto-alignment level to Do not align, and set Outline simplification level accord­ing to your pref­er­ence (we rec­om­mend Be very precise).
  8. From the Hints and Guidelines sec­tion, add the action Convert to instructions.[sin­glepic w=645 id=19]
  9. Choose Apply action to: All glyphs in the font or All opened fonts. Click on Run.

After com­plet­ing these steps, you have a basic TT-autohinted font. You can gen­er­ate your TrueType-flavored font now, or you can pro­ceed to fine-tuning the TT auto­hint­ing results.

4.3. Fine-tuning the TT auto­hint­ing results

To start fine-tuning the TT auto­hint­ing results:

  1. Open any glyph in the Glyph Window.
  2. Choose Tools / Hints & Guides / TrueType Hinting.
  3. In the TrueType Options panel, click on the icon so the TT Hinting Options dia­log will appear.

In this dia­log, you will find TT stems and TT zones that have been copied from the PS stan­dard stems and the PS align­ment zones. Edit­ing the TT stems may have sig­nif­i­cant impact on how con­sis­tently dif­fer­ent stems look, espe­cially in pure black-and-white ren­der­ing. For exam­ple, merg­ing some stem val­ues will result in a font in which the slightly dif­fer­ent stems will appear more consistent.

One impor­tant para­me­ter for TT stems is the ppm2 value. This value indi­cates the ppem size at which (mostly in black-and-white mode) the stems will turn from 1 pixel width to 2 pix­els width. (The ppm3 entry indi­cates the ppem size at which the stems will turn from 2 pix­els to 3 pix­els width etc.).

Low­er­ing those ppem val­ues will result in the affected stems appear heav­ier in small sizes. Rais­ing those ppem val­ues will result in the affected stems appear lighter in small sizes. For exam­ple, if you have a Medium style and a Semi­bold style in your fam­ily, and they look too sim­i­lar at small point sizes, you may choose to decrease the ppm2 and ppm3 entries in the Semi­bold style (so it will appear heav­ier), and to increase them in the Medium style.

This con­cludes the tutorial.

pages: 1 2 3 4

 

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