Giancarlo have you ever used the Java Advanced Imaging (JAI) library for the
scaling process? It is a fast library for working with images and it runs on
Windows, OS X and Linux (it has native libraries, but has failover to java code
if native libs aren't found). I considered it against ImageMagick and found
that I could get better quality images and in the same amount of time or
faster. It is definitely much faster than the JRE Java2D implementation, even
the failover java code I found to be noticeably faster than Java2D. I've used
it successfully in a couple of apps, both of them use it for scaling, rotation
and cropping of images. JAI supports a fairly wide range of image formats
(definitely the common ones: jpeg, gif, tiff, png) and converting between them
(my understanding is it uses the ImageIO lib that is in the JRE for the
reading/saving part, which in turn uses NIO for fast performance).
As far as the best scaling algorithm that I could find, the best one was to
scale an image down by no more than half of its image size at a time with a
final scaling that would put it in the correct resolution (that was the method
that came up most consistently on the JAI list when I was reading it). In
pseudo-code the basic idea would be:
Calculate imageScale from current size to final size
While (imageScale < 50%) {
scale image down by 50%
recalculate imageScale from current size to final size
}
Scale image by imageScale
I remember the first time I came across the method I ignored it because I
thought it would take so long to do scaling in multiple steps, but it is fast.
The interpolation method I used when scaling was bilinear. I found that small
details remained intact very well without odd pixelations. One of the apps I
did had professional photographers projecting the scaled images onto large
screens and looking at them with their clients. If there were issues with the
scaling method I used I think they would have told me.
Another method I read about had to do with blurring the image before scaling it
down once, but blurring was always much slower unless the image were so small
that it was going to be fast even if you did it using the Java2D lib.
Tom
________________________________
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of
Giancarlo F. Berner
Sent: Tuesday, December 02, 2008 4:01 PM
To: Magnolia Dev-List
Subject: Re: [magnolia-dev] Image (asset/document) management with
Magnolia
Hi Tom
Thanks a lot! Yeah, one approach is to upload images and use the
ImageMagick batch process.
I have spent quite some time on an algorithm for scaling images in
Java. There are many interesting approaches, but none is complete. The problem
is that you need several different "filters" to complete the scaling and my
imaging knowledge is rather limited. However, I did a lot of experimental work
and have a working solution, but the quality could be better. My "vision" is to
have a class which instantiates the image data and does different renderings
(e.g. rotation, scaling, etc.).
So if there is anyone out there who is wasting brain juice on the same
topic, maybe we could scratch our heads and come up with a neat Java API.
Thanks for your hint, Tom!
Giancarlo
On Dec 2, 2008, at 2:47 PM, Thomas Duffey wrote:
On Dec 2, 2008, at 4:27 PM, Giancarlo F. Berner wrote:
The real challenge here is to write a image scaling
servlet which renders photoshop quality images!
My suggestion for this part of the problem is to use
ImageMagick (Or GraphicsMagick, if you like) along with Runtime.exec(). I
tried to find something as awesome as ImageMagick but for Java and came up
mostly empty handed. Yes, there is JMagick, but there are several reasons why
you might not want to use it. Some of those reasons are described here:
http://www.darcynorman.net/2005/03/15/jai-vs-imagemagick-image-resizing/
Good luck!
Tom
On Dec 2, 2008, at 1:21 PM, David Smith wrote:
Speaking from the peanut gallery, I would
prefer the images be
pre-scaled and stored multiple ways in the DMS
myself as it speeds up
rendering to the public. Scaling on the fly
from a single copy to each
client is expensive on system resources.
--David
Jackson Nicolas wrote:
Hi Ole,
You seem to be receiving a lot of
responses but there's one I would
hope to read but isn't here. I was
expecting that the "Magnolia-way"
would be not store multiple instances
of the same image, but instead
one instance and be able to deliver
multiple instances on request. In
this case, you would not have to make
any changes to the DMS but
instead create a simple servlet that
can deliver varying instances.
Unless you REALLY do have a valid
reason to store multiple instances
of the same image, I don't see why you
should. Since you want to do
the resize on automatically on the
upload anyway, why not do it on the
download. Magnolia is great with
caching so you will only have to
resize once just as you would with the
upload.
I hope this helps.
Best,
Jackson
On Tue, Dec 2, 2008 at 11:35 AM, Ole
Christian Rynning <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
I am currently in a very early stage
evaluating Magnolia.
I need to import and manage several
thousands of product images
with the WCMS/DMS. Typically the
images are large jpgs, pngs, gifs
and pdfs. When importing I wish to
automatically resize the image
into three sizes: thumbnail, product
and large (+ full).
For this I wish to to develop a
module/template that:
A) Automatically resizes the images
and stores them into the DMS
i.e. under
images/products/name-{thumb,small,large,full} upon
upload/import.
B) A template that allows the editor
to navigate the DMS by
thumbnails, and insert images with
selected size.
Can anybody give me some general
pointers for how to do this (the
magnolia-way!)?
Best regards,
Ole Christian
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