Re: Using Dia for book illustration

[Lars Clausen <lrclause cs uiuc edu>]

On 15 Feb 2004, Gerard Milmeister wrote:
> Hi,
>
> I am the coauthor of the book "Comprehensive Mathematics for
> Computer Scientists" that will appear by the end April
> at Springer Verlag.
> We tried to use only open-source software to create the book,
> i.e., LaTeX2e ... I created some 70+ illustration, and Dia
> was the only open-source program adequate for this task.
[...]

Glad to hear it!  Makes it all worthwhile.

> To make some of the more complex (3D) drawings I created the graphics
> first in Mathematics then exported to PNG and imported it
> as a picture in a separate layer in Dia, and then traced the lines
> of the pixmap. This was a lot of work, but the quality it
> generated justified it.

That does sound like a lot of work.  Too bad none of the vector formats
could work for that (I assume you've tried them).

> I know that Dia has been designed for diagramming, but up to now it
> is the only program for Linux that is suitable for technical drawings at
> all (there being no Illustratorm and Sketch for example
> is awful at handling fonts). So I would like Dia to be extended
> to a full-featured illustration program, I think the potential is
> there. Here are some of my thoughts:

Technical drawings and diagrams are fairly close -- you'll notice the
number of technical shapes already here.  I'd like to stay away from the
more illustration-like things mostly (like gradients, curved text etc).

> 1. Rotation and Resizing of graphical objects.

High on my list.  Do you have a suggestion for an interface for it?

> 2. Alpha blending would be useful.

Yes, but would also slow do rendering, which, as you mention, isn't the
best already.  Also many formats do not support it, so exporting would be
even iffier.  Not a high priority for me.

> 3. More precise positioning including measuring. It is not easy
> to create two non-parallel lines of exactly the same length.
> Also there should be different ways to create
> circles and other objects, for example, by indicating the center.
> The grid is extremely useful, but snapping on the end of lines
> would be helpful too.

I've been wanting to have Dia show the dimensions of an object when
dragging it, that would be much usefu and shouldn't be too hard to
implement.  

Different ways to create circles... well, you could create a new circle
object that has its handles in different ways, but that seems silly.  Maybe
a new handle in the center so that you can snap to grid there, and/or an
option to make it resize from the center rather than the corner.

Interesting idea... snap to, but not connect.  Connecting lines to lines
leads to lines that cannot be taken apart:)

> 4. Font handling is good, but there should be minimal support
> for formulas, e.h., subscript and superscript, changing
> fonts within a text.

Right now half the text objects are just char*'s that the objects render.
Once they're all Text objects (which is required for other improvements),
we could make Text objects have some attributes.  There's just no end to
what attributes people would want.  An alternative is to finally make the
LaTeX interfacing object.

> I also noticed that font metrics on the screen don't
> quite match those in print, although this has been no
> real issue in practice.

That's because fonts don't scale linearly (except maybe PostScript type1).
We attempt to make them the same size (but see below).

> 5. I had some real fiddling to do because measurements (font sizes)
> are not absolute. There are three numbers I had adjusted:
> font size, scale in Dia, and scale factor in LaTeX's
> "\includegraphics"

Sorry to hear that's such a problem.  

> 6. The antialiased view is useful but slow (even on a 2400MHZ P4).
> Can this be improved?

It has been improved somewhat in the newest CVS, but I'm waiting for the
Pango people to supply a 'render text at this width' function.  Until then,
when rendering text at zoom != 100%, we have to render the text several
times until we get close enough, which is slooow.  In CVS, we cache that,
which helps quite a bit.  AA rendering is slower because there's more
alpha-work to do.

> Well, that's all I can think of now.
> So, thanks for the great piece of software, and continue
> with the development.

Thanks!  Since I now have a working home system again, I shall be able to
do more.  I'm very happy to get feedback, especially from people who've
used Dia for significant amounts of work, who know where the shoe is tight,
so to speak.

-Lars


-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| HĂ„rdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?