Error when using bitmap font embedded inside truetype font.

[jackyyf]

Truetype font has a feature which allows you to embed bitmap font for specific font size, to optimize the rendering results on screens. But using such fonts in Pillow will generate some strange result.

Example:

In this case I'm using a modified version of SimSun, which contains embedded bitmap fonts, for all size between 8px and 24px. In the image, first line is using 24px font and the second line is 28px.

TestCase is available (Contains SimSun font, testcode and the result above).
This test can be reproduced on both windows and linux.

[wiredfool]

Replicated here on Ubuntu 12.04 with Freetype 2.4.8. I'd like to find something that renders fonts using Freetype (other than Pillow) to see if it's a problem at the font/freetype layer, or something in how we're driving freetype.

[jackyyf]

I have a project in PHP, which is actually an image generator with this font at 14px using php5-gd library, and it works really great (using embedded bitmap font).

According package dependency information of debian package php5-gd, it depends on libfreetype6. So I think it's not an issue with freetype library :)

[jackyyf]

After some test, this bug exists since at least Pillow 2.2.2(earlier versions do not support freetype 6). All versions since 2.2.2 produced same image.

[jackyyf]

Found a dirty work around, adding FT_LOAD_NO_BITMAP to all FT_Load_Glyph load flags, which will let freetype avoid embedded bitmap font.

Found the solution at http://www.freetype.org/freetype2/docs/tutorial/step1.html