[Devel] Adding options to the PS Hinter

[Owen Taylor]

I've been experimenting some with applying only portions
of the Postscript hinting algorithm; in particular:

 - *not* snapping stems to integer widths
 - Aligning to BlueValues
 - Adjusting stem positions for maximum contrast

This has the effect of trading off contrast for reduced
distortion of letterforms. 

(See http://people.redhat.com/otaylor/fonts/hinting-screenshots)

I think these results are fairly encouraging; depending
on display conditions and personal preference, the results
seem to be better than either no hinting or full hinting
for a wide range of fonts and sizes.

A prototype patch is below, but it only allows adjusting
the options via changing some #defines and recompilaton;
if there was interest, I'd like to submit this change,
but I'm not really sure the right way of adding a runtime
option for this.

I suppose the simple way, and perhaps the right way, is 
to simply add another global load flag or two:

 FT_LOAD_NO_STEM_SNAPPING

And maybe:

 FT_LOAD_NO_VSTEM_HINTING

For the effect of aligning horizontal stems but not vertical
stems. (The samples show that that vstem alignment increases 
contrast quite a bit, but has some bad effects on interglyph 
spacing.)

It's quite possible that the same techniques would work
for the autohinter as well as the postscript hinter.

What do people think?

Regards,
                                        Owen

[ This work was inspired by David Chester's xfthack hack,
  if different in detail; the idea of aligning stems
  for contrast owes something to a comment by Raph Levien ]

freetype-2.1.1-partialhint.patch
Description: Text Data