[ft-devel] RE: dropout in '2' in times.ttf

[Graham Asher]

Please ignore this: I now have a fix, which is to turn off hinting when
anti-aliasing. It seems that the effect of grid-fitting the 2 (as I verified
by looking at it in FontForge) is to so narrow the stem that it can only be
rescued by dropout control; which doesn't exist for anti-aliased rendering.

The question still arises of how to sensibly apply hinting to anti-aliased
characters, which can still benefit from snapping stem widths to integral
pixels, particularly at small sizes.

Best regards,

Graham


-----Original Message-----
From: Graham Asher [mailto:address@hidden 
Sent: 22 May 2007 12:57
To: 'address@hidden'
Subject: dropout in '2' in times.ttf

Dear FreeTypers,

Here is a problem that has probably already been solved, given the
popularity of Times Roman.

Is there a solution for the really bad dropout in the digit '2' in Times
Roman (times.ttf) when anti-aliased? I enclose a PNG file illustrating the
problem at 16ppem.

Here are the actual pixel values generated by FreeType 2.3.4, as 11 rows of
6 pixels, in hex:

6 93 F0 E0 43 00 
2 65 0A 2D CD 2F 
6E 00 00 00 3D C5
0 00 00 00 06 EB
0 00 00 00 1F 9A
00 00 00 00 6B 1B
0 00 00 1A 3C 00
00 00 06 25 00 00
0 02 11 00 00 00
4 10 00 03 4E BB
B4 FF FF FF FF 88

Note the stem near the bottom has adjacent values 2h and 11h, totalling 13h
= 19; thus the stem has an effective horizontal width of 19/255 = 0.075
pixels, which is incredibly narrow. Naturally the pixels don't show up at
all.

Thanks in advance for any help or advice.

Graham Asher