[ft-devel] severe problems with subpixel hinting

[Werner LEMBERG]

Erik,


there are at least two serious problems if FreeType gets compiled with
subpixel hinting

  . B/W rendering sucks.  Attached you can find two images, with and
    without subpixel hinting, showing the font arial.ttf, version
    5.06.  I've simply called

      ftview 15 arial.ttf

    and pressed the `a' key to toggle anti-aliasing off.  According to
    the `gasp' table, this font must be rendered B/W at 15 ppem, so
    enabling subpixel hinting must not prevent the original hinting
    instructions if switching to bi-level rendering.

  . Subpixel hinting causes an extreme slowdown.  Running ftbench with
    arial.ttf, I get

      Load                      : 50.875 us/op
      Load_Advances (Normal)    : 50.945 us/op

    vs.

      Load                      : 724.595 us/op
      Load_Advances (Normal)    : 723.306 us/op

    Loading the font is more than 14 times slower!

Before enabling subpixel hinting by default, these issues *must* be
addressed.


    Werner