Howdy, Stranger!
Categories
- All Categories
- 39 Introductions
- 3.6K Typeface Design
- 764 Font Technology
- 1K Technique and Theory
- 587 Type Business
- 435 Type Design Critiques
- 526 Type Design Software
- 30 Punchcutting
- 132 Lettering and Calligraphy
- 79 Technique and Theory
- 53 Lettering Critiques
- 461 Typography
- 289 History of Typography
- 111 Education
- 61 Resources
- 479 Announcements
- 74 Events
- 104 Job Postings
- 147 Type Releases
- 153 Miscellaneous News
- 259 About TypeDrawers
- 52 TypeDrawers Announcements
- 109 Suggestions and Bug Reports
Options
Question about GPOS, GSUB
Wei Huang
Posts: 97
I came across some problems with my hinting on subscript numerals with ttfautohint—I assumed they would look the same as the superscript numerals but weren't—I asked for Werner Lemberg's advice and it turns out it was because I was using composite glyphs in the subscript (of superscript glyphs) and I didn't turn on the option to hint composite glyphs. He also offered the following:
Use the same glyphs that are in superscript for subscript—the same position and metrics and decomposed so they are outlines. Then I edit the GPOS table using the SinglePosFormat1 table to lower the subscript glyphs (and include device tables for ppem settings). This will keep the same hinting. Is this correct? I don't understand why it's better but I'm still awaiting a response.
Furthermore: there's an example at the GPOS page "Example 2: SinglePosFormat1 Subtable" which is exactly for this situation:
In general, shifting glyphs vertically is problematic. I think a better solution than ttfautohint's `-c' option in combination with composite glyphs is to use GPOS Single Adjustments to move (non-composite) glyphs vertically, where the Adjustments' ValueRecords hold DeviceTables for vertical placement – this ensures that the shiftI still don't quite understand Werner's advice but from what I understand I think it means this:
offset is an integer number of pixels (and not in design units), thus preserving the hinted shape because GPOS positioning happens after hinting.
In the previous paragraph, I'm referring to the OpenType specification for the `GPOS' table, cf.
http://www.microsoft.com/typography/otspec/GPOS.htm#SP
http://www.microsoft.com/typography/otspec/chapter2.htm
Use the same glyphs that are in superscript for subscript—the same position and metrics and decomposed so they are outlines. Then I edit the GPOS table using the SinglePosFormat1 table to lower the subscript glyphs (and include device tables for ppem settings). This will keep the same hinting. Is this correct? I don't understand why it's better but I'm still awaiting a response.
Furthermore: there's an example at the GPOS page "Example 2: SinglePosFormat1 Subtable" which is exactly for this situation:
Example 2 uses the SinglePosFormat1 subtable to lower the Y placement of subscript glyphs in a font.Why do the subscript glyphs need to be lowered: shouldn't they be at the correct position already when designing them? Or, is it implied that subscripts are activated by a GSUB that puts the superscripts glyphs in place of the default numerals and then lowers the superscript glyphs with a GPOS?
0
Comments