Hinting: lower-case 'm' missing pixel on centre stem (anti-aliasing off)

[David Owen]

Ubuntu Desktop 10.04, ubuntu-private-fonts-0.1.6~ppa4, multiple applications, including The GIMP and Firefox.

The gap appears from 36px to 47px. Below that range, the right curve looks smooth all the way into the joint with the left. Within that range, it looks like it misses a pixel at the bottom of the joint. Above that range, the missing pixels begins to widen out and look more natural.

All of this is with hinting turn on, full.

[David Owen (dsowen)]

Attached "m.png" shows the ends of the range, 36px and 47px.

[Vincent Connare (vince-daltonmaag)]

Hello, enclosed is an image showing the :

1. design of the lowercase m,
2. the rasterized lowercase m at 21 pt/ 120 dpi and 22 / 120 dpi.

The 'missing' pixel appears when the resolution is high enough to represent the curve in the original outline.

This break point starts at 36ppem which is equivalent to 36pt/72dpi; 27pt/96pdi, 22pt/120dpi

regards,

Vincent Connare
Dalton Maag Ltd.

[Matthew Paul Thomas (mpt)]

Belated thanks Vincent for that excellent explanation. So this is not a bug, just a case where very slightly less than half the pixel is covered, so with no anti-aliasing the pixel is unfilled. Even if that didn't happen at 36px, it would inevitably start happening at some larger size.