Re: VMs: .sid Viewers

[Gabriel Landini <G.Landini@xxxxxxxxxx>]

On Monday 07 June 2004 08:29, Nick Pelling wrote:
> At 15:52 06/06/2004 -0700, Clay Holden wrote:
> Gabriel, may I ask how suitable you think ImageJ is for working on
> MrSID-style (ie large, 24-bit colour) images? 

Hi, I also have been looking for a linux sid reader.  There seems that there 
is no sid reader for ImageJ so I have only downloaded a few JPGs (they are 
great). The program is superb, free, runs everywhere and it is extensible 
through plugins written in Java and it runs very fast.
The only problem is memory limits, so if images are too large and the 
procedures needed to process them require internal arrays to store more 
results, then one is very likely to run out of memory. RGB images have 3 
planes, so multiply the x*y size of each image by 3 (the f1r jpg is about 2.7 
MB, but internally IJ uses 91 MB!).

I have run IJ specifying 900MB of memory (hoping than swap memory will be 
used) and I can crop the image and do brightness/contrast corrections and 
split into an RGB stack, filter it and merge it back).
It copes with greyscale Ok specifying "only" 256MB of memory (I have been able 
to process various convolutions, sharpening, rank filters, etc. all at the 
original resolution).

For setups with less memory, two alternatives are to either trim and analyse 
regions of interest or reduce the image size.

> ISTM that many useful ImageJ
> plugins (perhaps because of a general stereology bias?) only currently work
> on 8-bit images.

That is not a problem. Many procedures that work on 8 bit images can be 
applied to colour images plane by plane. I guess that lots of plugins are 
said to work only on 8 bits because the extension to RGB is straightforward: 
convert the image into a RGB or HSB stack, process the stack and then merge 
them back again into a colour image.

Cheers,

Gabriel

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