Up: WebEQ Documentation

Making WebEQ Fonts

The WebEQ system downloads its symbol fonts in blocks of 10 as necessary. If a collection of web pages all access the same copy of WebEQ as specified by the CODEBASE parameter of the APPLET tag, WebEQ will share symbol fonts, minimizing download time.

WebEQ symbol fonts require two files for each block in 7 sizes.. These files are named symX-pY with .gif and .tab. extensions. The symbol fonts are contained in blocks of 10 symbols. The number in the X position denotes which font block. The number in the Y slot denotes a size. Each font block is generated in 7 sizes, with 7 being the largest.

Each symbol set requires a .gif image file containing a transparent bitmap of the symbols, and a .tab file specifying offset and alignment data.

The .gif file contains 10 lines with one symbol character on each line. WebEQ clips symbols out of this .gif file and then positions the resulting character box on the web page. The .tab file contains parameters for both the clipping process and the page positioning.

A typical .tab file looks like:

#Symbol Font -- block 3, size 5
#Wed Mar 20 17:07:10 CST 1996
1020=34 0 17 16 29 0 2
1021=34 0 23 16 29 0 2
1022=34 0 29 16 29 0 2
1023=34 0 35 16 29 0 2
1024=34 0 41 16 29 0 2
1025=34 0 47 16 46 0 2
1026=34 0 53 16 46 0 2
1027=34 0 56 18 32 0 2
1028=34 0 56 30 14 0 8
1029=34 0 62 30 14 0 8

The numbers 1020, 1021, etc are character values used internally by WebEQ and should not be changed. After the = must follow 7 space separated integers, for example 34 0 17 16 29 0 2. In order these numbers mean:

34 -- this number should be the baseline skip in pixels between lines in the . gif file.
0 -- this is a horizontal clipping offset. This number shifts the location of the clipping window left and right.
17 -- this is a vertical clipping offset. Changing this number shifts the location of the clipping window vertically. Unfortunately, computer graphics coordinates are in effect so a positive shift is downward.
16 -- this is the height in pixels of the clipping box.
29 -- this is the width in pixels of the clipping box.
0 -- this is the horizontal offset of the symbol's bounding box in a line a text. Changing this more than a pixel or two results in symbols overwriting surrounding characters. However, in certain cases, shifting a pixel or two will alleviate a particularly bad italic deviation.
2 -- this is the vertical offset or descender of the symbol's bounding box.

Making User Fonts

WebEQ provides character codes for a user symbols block. These entities are accessed by the names &user0 ... &user9. WebEQ will look for this font in sym9-p?.

Users can generate their own fonts by creating the 7 necessary .gif and .tab files. The simplest way to do this is to modify one of the TeX source files in the /mkfonts directory, compile it with AmsTeX, look at the output with Xdvi or a similar previewer, and use and image processing program like xv to make a .gif snapshot of the output. Then, using a test file such as testf1.html in /mkfont create and edit the corresponding .tab files by hand. This is laborious, but straight forward.

Alternatively, sophisticated users can try to modify the make-font script by Davide Cervone in the /mkfonts directory to run on their systems. This script automatically generates the necessary .gif and .tab files. However, it contains many features specific to the Geometry Center somputer system at this point. Among them

dvips must be able to generate fonts at arbitrary pixel densities via the -D option
The ghostscript program gs is used
The ImageMagick program convert is used
A special purpose Geometry Center script img2gif is used to turn the background transparent
And of course, the script is in PERL

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Comments to: rminer@geom.umn.edu
Created: Fri Sep 8 11:39:00 1995 --- Last modified: Thu Mar 28 12:44:51 1996