Re: Problem with mis-identified .png graphics files when generatingDVI

["George N. White III" <WhiteG@mar.dfo-mpo.gc.ca>]

TeX and related tools have become a massive system that is becoming a
signficant problem to maintain. It is easy to say "let's just add support
for the new XYZ graphics format" to dvips or pdftex or xdvi or ... These
suggestions are rarely accompanied by the necessary patches. In practice,
adding support for new graphics formats involves linking to 3rd party
libraries, changes to macro packages like LaTeX and ConTeXt, etc. There
are other urgent needs (e.g., UTF-8/Unicode support).

Support non-native graphics formats in pdftex and dvips should be viewed
with caution. It is important to note than the support in pdftex for PNG
and other image formats is incomplete, and that the most reliable
method to insert images into PDF files is to make the images into PDF
independently of pdftex. With dvips, the most reliable approach is to
convert images to EPS. Adding support for images to pdftex has resulted in
a more complex program that is less portable and less immune to side
effects (e.g., changing a .dll or .so version) from other differences
between similar systems.

In my work (which involves processing remote sensing data commonly
visualized using "false color" images), it is important that similar
images always have consistent color scales. I view the image support in
pdftex as a convenience (e.g., if it works well enough for a particular
project, I will use it, but I would never rely on it for critical work).
There are many attributes of PDF images that you can't easily control
using the support provided in pdftex, so images "placed" using PNG rarely
match the colors of images converted to PDF using other tools.

The problem reported by Bruce Horrocks would not arise when using EPS with
dvips and PDF with pdftex.

-- 
George N. White III <gnw3@acm.org> Bedford Institute of Oceanography