I am embarking on teaching myself to use GIMP in the hopes that I can use it to develop tutorials for space image processing for the Society's website, but of course I have questions. Does anybody here use GIMP on a regular basis and have any useful tips? I was happy to see how much of Photoshop's functionality it appears to mimic, but I'm a bit nonplussed to discover that it can't deal with 16-bit images, only 8-bit.

I did find a plugin for opening PDS images (http://registry.gimp.org/node/1627), but it seems to choke on Cassini images (perhaps because of the 8-bit problem, I'm not sure).

I have figured out how to take three grayscale image files and make them into a single RGB image (through Colors > Components > Compose...)

Does anyone know of a good plugin for automatic alignment of images?

Any other tips?

--Emily

I use GIMP fairly frequently but I'm not doing any sophisticated image processing.

As a suggestion, I'll just point out that functionality can be appended to GIMP distribution using the Python scripting language. If you're looking to make an open-source and multi-platform tool, this is a nice situation. Python with it's SciPy/NumPy modules would be very powerful and concise for image processing.

http://www.gimp.org/docs/python/index.html

Without wanting to start an off-topic religious war I will only point out that there are tons of GIMP-related stuff for Perl, as well; basic Perl with GIMP tutorial here, GIMP-related Perl modules, generic graphics modules and a selection of mathematical stuff.

When I dig my way out from under few dozen MSLs[1] of pre-audit ISO hell (don't ask) I'll be writing some trivial Perl / GIMP code for visualising network maps, -- very trivial in comparison with processing astronomical images, of course :/

As a card-carrying swivel-eyed Free software zealot, I'm sorry to say GIMP has a pretty poor reputation. I'm sorry we don't seem to have anything much more powerful; traditionally GIMP's been all there is. Thankfully there's now Inkscape, an alternative for vector-related image work (think Illustrator to the GIMP's Photoshop) - much better for diagrams and the like; and FWIW, I googled up these related Free software projects:

Pixia, another bitmap processor - this is an internationalised Japanese app;
PlanetGenesis - like Terragen;
Hugin - like AutoStitch;
...and Wikipedia has a list of various graphics apps, including other Free ones I've not mentioned (or indeed heard of )

[1] Alternative volumetric unit to VW Beetles

Yeah, it's not looking particularly promising. I'm not finding GIMP very intuitive, but that may just be because I'm so used to Photoshop that anywhere that GIMP doesn't work precisely the same, I'm at a loss. Still, I'd like to be able to write tutorials that people who can't afford Photoshop can use. Maybe I should write tutorials first in general terms (but terms specific enough to allow readers to Google for how to do the described operations in their image processing software of choice), and then provide specific versions for more than one piece of image processing software. That sounds like a lot of work though. I'm beginning to think that what I need to do is build a wiki and try to cajole expert users of one piece of software or another to contribute content.

--Emily

Having never spent much time in Photoshop, Gimp has been a faithful albeit frustrating companion to my exploration of the rover images. I haven't spent much time working with plugins or scripting within gimp, although I do use Python/PIL/Numpy on its own for all my image processing scripts. But, at the end of the day, gimp easily handles the 'finishing touches' on images before posting them online. For simple things like cropping, resizing, GIF animations/compression, etc. I've found gimp to be easy to use.

Emily, I'd be a willing cajolee if you were interested in doing a wiki-style guide. You could list out the tasks you were interested in including on the page, and I'd be happy to writeup the ones with which I'm familiar.

How about Photoshop Elements. It's V cheap ( <10% of Photoshop ) and is essentially, Photoshop with the pro stuff taken out. It might do the job.

Doug

"...How about Photoshop Elements. It's V cheap ( <10% of Photoshop ) and is essentially, Photoshop with the pro stuff taken out..."

Elements is the kiddie-school dumbed-down and stripped version of Photo"slop". It's got some nifty consumer stuff, but it lacks stuff Photoshop 2.5 had under Windoze 3.1. Most catastrophically, from my viewpoint, it has no ability to separate and / or merge color channels.

That sounds about right, I conversely, I often get frustrated with not being able to work out how to do something in Photoshop and end up firing up GIMP instead.

Ahh - that's a no then. I've used Premiere Elements - and it was very good compared to Premiere. Pity.

Doug

I use Elements and love it, but t'is true, it can't separate / combine colour files... that's why I do my RGB work in Paintshop and then "tweak" - sorry, carefully change - the images in Elements afterwards...

Do you find the lack of support for 16-bit images a limitation?

No, not really, but to be honest I only really do finishing touches in GIMP/Photoshop.

Nearly all my MER image processing is done using home grown routines, within those I'm storing data at 32-bit depth. I wouldn't want to do any serious processing of images at 8-bit.

James

I tried GIMP, but I quickly returned to Photoshop. Due to the nature of how it was/is made, GIMP is extremely inconsistent. BTW James, I know what you mean about bit depth. I usually work in 16 bit grayscale and color, and have occasionally done a whole lot of work, only to find that I had done it in 8-bit mode. The amount of loss is crippling.

That's what I figured; I couldn't imagine you were doing much real work with images stored at 8-bit depth. But there's no harm in showing newbies how to do it, letting them catch the image processing bug, and then telling them they need to pay for some better software, or write their own.

Anyway, here are the most basic image processing tasks that I'd like to cover:

- Making RGB images from three single-filter images
- Making red-blue anaglyphs from right- and left-eye images
- Aligning three Voyager or Cassini images so that they may be combined into an RGB combo
- Making simple animations (e.g. Hazcam movies, Voyager flybys, Cassini mutual event observations)
- Making a simple two- or three-image mosaic (focusing mostly on the basic tasks of enlarging the canvas, aligning images, and adjusting levels, not considering more complex stuff like warping images to account for changing perspective)

I have a single tutorial written, for aligning images and making an RGB combo, using Photoshop and Elements:
http://www.planetary.org/explore/topics/im.../tutorials.html It'd be easy to modify that one for other software, if I am sent appropriate screen caps and a description of how the workflow diverges. I think I may separate the alignment and make-RGB parts of this tutorial.

There are a lot of other related topics I'd like to cover, such as: where to get data from each mission; how each mission's instrument functions; software for auto-stitching and auto-aligning; etc. But these tutorials would be a good place to start.

--Emily

ImageJ is a free NIH application which will allow you to split and combine color channels, even using arithmetic combinations. Also lots of free plugins for specialized image processing.
http://rsb.info.nih.gov/ij/index.html


Stereo Photo Maker (also free) is very good for creating stereo images (whatever the format), and also allows you to align (rotate/translate/scale) the images with respect to one another.
http://stereo.jpn.org/eng/stphmkr/

This book is a bit old, but provides a lot of useful information on basic and advanced features. Grokking the GIMP.


Paolo Amoroso

GIMP 2.6 adds support for 32 bits per color channel.


Paolo Amoroso

That's great news, thanks for the heads up. I'll have to take a look at using it again.

--Emily

w00t!!! imipak: does a little jig of delight, before pausing to genuflect towards the bust of RMS

For Macintosh users, there is a .dmg compiled here : http://gimp.lisanet.de/Website/Download.html
The integration to the UI (leopard for me) is pretty good

I am doing that right now. If there is enough interest I will be releasing my code to the public domain in the coming months. To not hijack this thread please send any inquires to me via a PM. Eventually I will probably announce the project here, in it's own thread, of course.