exit driver

### Driving the Translation of Pictures and Other Tasks

TeX4ht outputs a script file (‘.lg’) describing how the dvi file (extension ‘.idv’) of pictures should be processed, the CSS instructions to be included for the file, and user-initiated requests from the operating system. In the default setting, the script file holds abstract commands similar to the following ones.

--- needs --- source.idv[i] ==> target.gif ---

  An abstract command of this form requests that the i’th page in the dvi file will be translated into a target file whose name is provided.

--- characters ---

  This abstract command is a identifies where the requests for pictorial characters start.

A manual brute-force execution of the abstract commands can be a tedious job for large number of pictures. The t4ht is in essence an interpreter for these abstract commands.

Another possible approach for automating the process is to request lg scripts in the form of shell scripts or batch files.

Alternatives to ‘--- needs --- source.idv[i] ==> target.gif ---’

The default setting is made with a request of the form ‘--- needs --- %%1.idv[%%2] ==> %%3.gif ---’, where the parameters %%1, %%2, and %%3 respectively represent the name of the source file without its extension, a page number, and a name of the target file. Alternative patterns to these abstract commands can be requested in the following locations, with the order reflecting on the priority given to the requests.

- In the command line of tex4ht, where the pattern should be prefixed with ‘-s’.

- In the environment file tex4ht.env within a block of consecutive lines, where the lines should be identified with the character ‘s’.

- In tex4ht with the pattern provided through the variable LGPIC of tex4ht.c.

The character ‘%’ can be introduced into a pattern through the entry ‘%%%’. On the other hand, the parameters ‘%%1’, ‘%%2’, and %%3 can specify, between the first two percentage characters (i.e., ‘%...%1’, ‘%...%2’, and ‘%...%3’), any format for the outcome that is compatible with the print formats of C.

Alternatives to ‘--- characters ---’

Substitutions for this abstract command can be requested in the following locations.

- In the overview of tex4ht, prefixed with ‘-b’.

- In a line within the environment file ‘tex4ht.file’, where the line should be identified with the character ‘b’.

- In tex4ht with the substitution provided during compilation time through the variable LGSEP of tex4ht.c.