On Sat, Jun 30, 2012 at 9:30 PM, Calculemus wrote:

Hello,

I am interested in contributing image processing algorithms to GIMP.

I need advice where do I find resources. I need book recommendations, where to find papers, or any other resource to study from.

Hi,

Personally I'm a bit puzzled. What specifically do you mean with "contributing image processing algorithms to GIMP"?

Writing arbitrary C code for image processing is probably not a good idea. But if you are interested in contributing to the project, there are several areas we'd be grateful for help in. Most image processing will now be happening in GEGL (www.gegl.org) which is used by GIMP.

There always are filters to be ported to GEGL operations, new GEGL operations to write, existing operations to be ported to use OpenCL for hardware acceleration etc.

Alexandre Prokoudine http://libregraphicsworld.org

Well,

There is this list where we are trying to keep track of what we do:

http://wiki.gimp.org/index.php/Hacking:Porting_filters_to_GEGL

We have two Google Summer of Code students this year working specifically on that porting, so you'd need to check back with them regarding their plans.

However there are too many filters to be ported. So we'd need every person willing to contribute.

That page has some intro docs. Feelk free to ask questions. For closer communication it's best to hang out on IRC, either #gimp or #gegl.

http://www.gimp.org/irc.html

Alexandre Prokoudine http://libregraphicsworld.org

On Sat, Jun 30, 2012 at 10:22 PM, Calculemus wrote:

Since I have had an image processing and computer vision course and interested later in Masters in the area, I am mostly interested in implementing image processing algorithms, in this case as you say "new GEGL operations". Where can I find ideas/suggestions what needs to be done?

Thanks for the quick responce ;)

You sent it off-list again :) "Reply to All" would help :)

The text means that you read source code (and code comments) of an existing GIMP filter, then rewrite it into a GEGL operation. AFAIK, some filters do mention papers they are based on, and some don't, but many of the latter are generic enough. E.g. some rely on other common algorithms such as convolution matrix.

Some of the filters have quite customized UI, e.g. the Flames plug-in. In that case it's OK to just port the back-end so that proper UI could be written later when we figure out how to do that. Right now all ported ops in the Git master branch use the skeleton of the "GEGL op" tool.

I suggest you have a look at the code of some simple existing GIMP filter that has already been ported to a GEGL operation. E.g. "Whirl and Pinch":

http://git.gnome.org/browse/gimp/tree/plug-ins/common/whirl-pinch.c?h=gimp-2-8 http://git.gnome.org/browse/gegl/tree/operations/workshop/whirl-pinch.c

Alexandre Prokoudine http://libregraphicsworld.org

On Sat, Jun 30, 2012 at 10:38 PM, Calculemus wrote:

Wow the filters list is big. It is exactly the thing I want to work on.

I am just confused about "Read the plugin you want to port, understand the algorithm hidden in it. ".

So this is already done in GEGL and basically you want to use it in GIMP? Or they are not implemented anywhere and I am supposed to know the algorithm and do it from scratch?

I have done a whole book on image processing algorithms, I can tackle this one and probably do more than the two GSOC students together :D

Am 08.07.2012 10:20, schrieb Calculemus:

I need to implement compositors for a project I work on, such as soft-light, hard-light, overlay, etc. like the ones in Photoshop. I see gegl has all those. But they use different math than the one I see in the original Adobe reference that is used for Photoshop and After Effects. To make things worse, on the web you can find even other approaches for the same operation, like soft-light for example. Someone can shed some light on this?

for a quite comprehensive comparison of many, many blend modes -- including several softlight formulas -- you might want to check out my article [1].

The big table [2] at the beginning of the article features the comparison list. In the link section there is also a site with ready-to-use C code, IIRC.

best regards, yahvuu

[1] http://yahvuu.wordpress.com/2009/09/27/blendmodes1/ [2] http://yahvuu.files.wordpress.com/2009/09/table-brightness-1600b.png