Issue #10

2007-April-26

Cheap, High Quality Fonts in Squeak

One of the very few things I don't like in Squeak is font support. I'm used to nice subpixel rendered text. I find StrikeFonts and TTFFonts in Squeak equally ugly on LCD monitors.

I have been a long time admirer of Henrik Gedenryd FreeType work, now continued by Andy Tween. But Andy's image requires linking the FreeType library, and a new BitBlt plugin with newer modes to work.

Something smaller and simpler needs to be done! Something that could look like this:

Why not just use StrikeFonts, but with 32bit glyphs? Why not just take already rendered glyphs from the host OS, instead of rendering them with FreeType?

This started as an experiment. I modified existing instances of StrikeFonts to use 32bit forms for glyphs. But it didn't work. So I fixed several issues there. I wanted to import the glyphs from the OS. Using a BMP file sounded natural. But it would be cumbersome to have extra parameters for the creation of the fonts. So I came up with a format for StrikeFonts that is contained in the BMP file. This is an example:

With this format, it was pretty easy to have a basic 32 bit font working. The issues that needed further work are:

Colored text and Black text on color (non white) backgrounds.

For Black text on colored backgrounds I started experimenting with alpha blending (BitBlt rule 34). But I realized that rule 28 could do a much better work. Rule 28 takes the min value between source and destiny for each rgb component. So it will leave the background untouched except for those pixels where the font wants something darker. There, the font rules. It looks great.

For doing subpixel AA of colored text on colored background I believe you need to render the font again. As I can't do that, I use whole pixel AA (i.e. regular AA). So I prepared color maps. For example, to render a red font, I prepared a colormap that maps the different colors in the font to red with different translucency. Then I display the text with alpha blending (BitBlt rule 34).

What's missing from a full solution, such as FreeType?

- No modelling of the fonts themselves

- No way to tweak the rendering other than editing the BMP files

- no kerning (fixed width for each character)

- Colored text doesn't use subpixel rendering

- Poor automatically generated italic (although you can import nice italized fonts)

Advantages:

- Very compact. Very little complexity added to StrikeFont

- Very easy to build your own glyphs or entire fonts

You can get the code and sample fonts here. After loading, execute:

TextConstants at: #Vera put: (TextStyle fontArray: (Array

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera7.bmp') name: 'Vera 7')

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera8.bmp') name: 'Vera 8')

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera9.bmp') name: 'Vera 9')

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera10.bmp') name: 'Vera 10')

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera11.bmp') name: 'Vera 11')

with: (StrikeFont new buildFrom: (Form fromFileNamed: 'Vera12.bmp') name: 'Vera 12')

))

BTW, if you get my morphic 3.0 image, it has this loaded. I also got rid of TTCFonts. And the image is now 3.6Mb!

I hope you like it.

Juan Vuletich