Will, you hit a topic, I just recently decided to solve once and
forever. I am spending lots of late nights digging my self through the
mists of digital image processing.
While yes, Java offers classes and methods to scale images, they
usually concentrate on speed rather than quality. I noticed weird
behaviors, e.g. I had a 350k jpeg image, past it through my test
script with NO scaling and got an image with about 250k in size and
slightly worse quality!
Java 6 seems to offer better image processing packages, but I did not
dig into that yet, since Java 6 might not be on most machines yet.
My challenge is to scale an image (yes, I am already happy if I can
"only" scale at a high quality) of different formats (e.g. jpg, gif,
png) with one package. I have a solution which is ok, and maybe I am
trying to reach for the sky, but I still am sure by tweaking the
algorithm I can achieve better results.
My 2cts: Scaling down requires "removing pixels". So if you just scale
down from e.g. 640x480 to 160x120 in one "swoosh", quality is worse
than if you scale in multiple steps. If you scale up, you have to add
pixels and it's a similar issue. If you do it in one "swoosh", quality
will not be as good as if you do it in multiple small steps.
However, many blogs nag on the multiple steps because that affects
performance.
Well, I am still on this topic. I will keep you updated.
Cheers
Giancarlo
On Mar 10, 2009, at 3:55 AM, Will Scheidegger wrote:
Well, JAI seems to be the solution, but as I said: I have yet to
find an example based on JAI which produces high quality results
with a wide range of image sizes without any funky side effects...
-will
On 10.03.2009, at 11:46, Peter Götz wrote:
Thanks for the article URL. Maybe there is hope and a way to get
image manipulation without having to use ImageMagick. I know the
pains you know, Will, and I would be glad to get them solved. :)
Peter
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----- Original Message -----
From: Will Scheidegger
[mailto:[email protected]]
To: Magnolia User-List
[mailto:[email protected]]
Sent: Tue, 10 Mar 2009 11:18:30
+0100
Subject: Re: [magnolia-user] OT: Image scaling algorithm
Thanks Peter and Tobias for the quick replies.
We've used ImageMagick before with good results - it's just really
hard for me to believe, that I need to talk to a C program over JNI
only to get a decent scaled image. And since this makes the
installation of webapps on servers a pain it's no real option for
us.
We've also used "getScaledInstance()" in Java. But apparently one
should not go that way.
http://weblogs.java.net/blog/chet/archive/2007/04/dont_use_getsca.html
The more you google the more opinions you get on that topic ;-)
-will
On 10.03.2009, at 10:48, Tobias Reinhardt wrote:
Hi Will
The following article explains the different pitfalls for image
scaling with java quite well. And it includes some code how to do
it
right. I don't know if it is the best solution, but it is enough
for
me.
http://today.java.net/pub/a/today/2007/04/03/perils-of-image-getscaledinstance.html
If you use the multistep scaling flag of the provided helper
method,
ensure that your server has enough memory.
Tobias
2009/3/10 Will Scheidegger <[email protected]>:
Dear Magnolians
This is quite off-topic, but I'm sure many of you have been faced
by the
same problem: Image scaling in Java.
I tried many different methods, googled for hours if not days, but
either
I'm getting low quality results or the thumbs have other "side
effects" like
a black border on one or two sides...
Does anyone have the definite solution to a problem which really
should not
be rocket science? I hate it when things are oh so easy in
Typo3 :-/
Thanks!
-will
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