Re: Figure formats

[Ville Voipio <ville.voipio@kpatents.com>]

> them to the picture itself. I also turn my CorelDraw pics into pdf 
> before adding them to ConTeXt based text, that inserts them nicely and 
> makes it easy for me to share any graphics at request (I'm occasionally 
> asked to send just graphic 3.1 from manual x, so it is a good thing to 
> have all of them as pdf).

An interesting thing is that sometimes some programs make stupid
mistakes when exporting to PDF. For example, I have had some
bounding box problems when exporting to PDF. The bounding box
tends to be the size of a page, which is really not a nice thing.
(This happens with CorelDraw 11 in OS X and with older CDR
versions in other OSes.) Illustrator should be safe, as PDF
is one of its "home" formats.

A workaround which I've been using for years is to export in EPS.
All graphics programs I've come across have been able to do that
reliably. Then the EPS can be converted into a PDF by using one
of the following: a) Adobe Distiller b) Ghostscript (epstopdf,
eps2pdf, or equivalent) c) Preview in OS X.

I have found it very useful to have all illustrations in PDF
format in the right size (i.e., clipped to the right size,
correct bounding box). Then it is easy to play around with them.

Even though vector graphics is -- in theory -- infinitely scalable,
in practice it is much better to try and draw the pictures 1:1.
If the images are scaled, line widths and annotations are scaled,
too. Especially when there are several similar pictures with
different scale factor, the result looks odd. So, the final size
of the illustration should be known before drawing the actual
picture!

It is also a good idea to scale the bitmaps down (or up) to the
final size and resolution before inserting them. This avoids
a number of strange problems when rendering the images. For
photographs, 200 dpi should be enough almost always, line art
requires 300 dpi. (And a very important exception is that all
screen captures should be taken "as is" without any operations
on them.)

Too large a resolution makes the files unnecessarily large and
slow, so even that should be gotten rid of. Graphics packages
have different resizeing algorithms, and getting to know all
of them takes some experimenting, but it is well worth the trouble.

What comes to the figure formats, PNG is good for lossless images
(screen captures) or images requiring alpha channel. JPG is best
for photographs and other continuous-tone real-world images
(and some visualizations). But, whenever possible, use PDF, if
there is any choice.

- Ville