Making Pictures and Diagrams

Making Diagrams

The best program in the Unix environment for making pictures is `xfig' a public domain program which has the wonderful property of being able to export pictures in PostScript form. Since we can import PostScript into LaTeX and therefore use Latex2HTML to process the file, we can obtain a high degree of versatily with respect to included diagrams, etc..
Here is an example of a LaTeX file which imports a PostScript drawing (from xfig), creates equations, etc..

\documentclass{article}     
\usepackage{epsfig}
\begin{document} 
\begin{figure}
	\begin{center}
	\fbox{ 
	  \epsfig{width=3in,file=pot_E.ps}
	}
	\end{center}
	\caption{Potential Energy Curves for Diatomic Molecule Undergoing PhotoDissociation}
\end{figure}
In the photodissociation of a homo-nuclear diatomic molecule, the exciting photon's
energy is 28,000 $cm^{-1}$, and the dissociation energy of the molecule is
25,413 $cm^{-1}$.
If the atomic mass of the nucleii is 16 grams/mole (i.e. oxygen), and if the
velocity of each of the oxygen atoms are equal in magnitude, compute the
value of the velocity of the resultant oxygen atoms when the internuclear
distance in infinite.
Assume that the molecule was initially at rest (we actually compute the 
velocity relative to the center of mass).
Report your answer in cm/sec.

\end{document}

What we do is to use latex2HTML to convert this LaTeX file to an HTML file. B B Then we take the resultant html file and convert it to a Perl script, adding whatever is necessary to allow student inputting of answers. What a drag.

Making Diagrams directly as gifs.

An alternative is to export the xfig drawings as gif files, which works,but is cumbersome for large drawings. However, such gif files are not ``transparent'', i.e., they are not in the best shape for viewing on the WWW, and other methods should be explored.

Mention should also be made of xpaint, another gnu free program which does the more primitive kind of non-object oriented painting. For most technical work, xfig is superior to xpaint.

Making Pictures

Assuming you have scanned in a picture and saved it to disk in some format, you can use ImageMagick to convert it to a gif or jpeg file, which can then be displayed using

<img src=../name_of_pic.gif>
or
<img src=../name_of_pic.jpg>

One should be aware that several symbols which scientists routinely use are not available on the WWW, and we need to supply them ourselves. For hydrogen chloride, one could write HCl, but the last letter looks poorly on the screen, and can be confusing to beginners. It is better to write HC

, which emphasizes that the last character is an `ell'. We do this here using

<img src=../icons/ell.gif> ->

where we constructed the image itself using Latex2HTML.
Consider writing a heat of reaction, i.e.

H_f^o

<img src=../icons/Delta.gif>H<sup>f</sub><sup>o</sup>