[NBLUG/talk] Re: ImageMagick

Steve Smith sjs at sonic.net
Sun Aug 8 13:46:14 PDT 2004

> eek.  You're ahead of me here.  I don't really understand the
> differences between the various image formats, although I know some
> have certain advantages over others.
It does make a difference.  Different formats compress in
different ways, and some don't compress at all.  If I use convert
to create a .png file, the characters look nice and crisp.  With
jpeg and same arguments, I have this gray shadow around the
characters. It could be the file format or an artifact of the
conversion process, but they are different.  When I create graphs
or charts, typically I use .png because they are easier to create
with a program -- simpler format.  Cameras and high-end graphics
typically use Jpeg -- at least that's been my experience and I've
been doing this kind of stuff for a while.

Also, many image formats have both an image and a canvas I
believe. The image is the graphics data and the canvas is what
the graphics is displayed in/on.  The canvas can be larger or
smaller than the image and the image can be offset within the
canvas.  It's something you won't encounter unless you're editing
graphis files.  And I had an excellent book I bought from O'riely
which is probably out of print now and which I can't find that
would probably explane exactly what I mean.

> as a follow-up:  I tried playing around with a .ps file and
> treating it as an image and it choked up my box pretty good.
> Perhaps the problem you are having *is* due to the original
> file format. (?)
> -dave.
Ain't learning curve wonderful.  For png, convert -crop
works fine but for .jpeg, convert hangs eating up all the
cpu it can get.  If i '^C it, I have 10 .jpeg files that
look fine.

Anyway, after thinking all of this over, I may use .bmp
because I want to use the same program on both windows and
linux.  I need to see what PERL/TK does best on both
platforms and how ImageMagic works with .bmp files.

Thanks again...
Steve S.

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