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Re: [Gimp-developer] I am hoping to contribute to GIMP. I have some ideas, but I want input if possible.

Hi,

On Mon, Nov 18, 2013 at 12:09 PM, DeVonte Applewhite <dapplewh nd edu> wrote:

Thank you for your response. We have used your input to clarify our
direction on this project. What do you think of this.
1. We will try to make a c++ implementation of gimpvector where we overload
operators and try to string the executable together so that it compiles.


As Sven also answered on the mailing list, GIMP is written in C, not
C++. And even though it may happen that some components may be written
in C++ if really it helped somehow (for instance when using some third
party library in C++ which is the best at what it does), I'm pretty
sure our maintainer won't accept any base class in C++, especially for
no reason.

Now if that's just for the fun of the experiment and the sake of your
class project, go ahead. :-) But don't have your expectations too
high, because such code may never make it upstream.


2. We will try to make a c++ implementation of gimpmatrix where we overload
operators and try to string the executable together so that it compiles. We
will also see if we can generalize some of the code that implements
operators.


Same as above.


3. We will attempt to fix at least one bug. If we can handle that, we will
try to do more bugs given enough time before the project's due date.


Cool.


4. We are trying to add a new feature to Gimp. It will be something small,
but we still want to do something that will be interesting. We were thinking
of looking into the filters or brush shapes to see what can come of that.


I understand that bug fixes are not sexy and you want something cooler. :-)
Well there are so many wanted features that it is hard to give advice.
About brush, I know there are some plans on supporting more brush
engine (in particular by using libmypaint, if not mistaken). Maybe
that's a path to follow if you want to improve brushes?
You may have an idea of the biggest planned features there:
http://wiki.gimp.org/index.php/Roadmap
Though if you have other ideas, we are always happy to consider
interesting new concepts.

But the best would be to come on GIMP's IRC where most of the devs are
hanging around (respectively in their timezones): #gimp on
irc.gimp.org
There you may ask questions if you have any, if you don't understand
something, or want to propose, etc.


We understand that this will not increase the speed of Gimp, but it may be
something else entirely that may be helpful to someone by chance (as we said
in our initial plan).

Thanks for this dialogue. It has been quite helpful to us moving forward.


You are welcome. Don't hesitate to come hang around on IRC. There is
no reason to just stop the dialogue. :-)
In any case, for the sake of the class, I understand that you have to
work fast and just implement "something to show your teacher". In this
respect you may not care too much about discussing too much about the
best approach and waste time. If that is the case, I fully understand.
Just be aware that some things are doomed from the start though (like
rewriting base class in C++ as you propose) if the goal is also to
merge upstream. Since I find it sad to waste good work and would
definitely prefer to see new contributors with upstream patches, well
I want to make sure you got this part.
In any case, have fun GIMPing! And maybe see you on IRC. :-)

Jehan


Have a great day.


On Tue, Nov 12, 2013 at 4:39 AM, Jehan Pagès <jehan marmottard gmail com>
wrote:


Hi,

On Tue, Nov 12, 2013 at 5:30 PM, DeVonte Applewhite <dapplewh nd edu>
wrote:

Hello all,

I am in a Data Structures class which has a final project. This project
requires students to fix bugs, improve preexisting data structures, or
add
extra features to an open source project that has an active community.
My
group chose GIMP.


Nice choice! :-)


I have some ideas about changing data structures in hopes
of generalizing some implementations, improving execution speed and
reducing the amount of code needed to complete implementation of the .h
files.

Here are 3 of our ideas. If you could give input (feasibility, faults in
our plan of action, predicted improvements upon success of these ideas,
suggestions) on any or all of our ideas, that would be greatly
appreciated.


Well I won't comment all the ideas in detail, and my guess is there
are few chances others will either, because that would take quite a
time! We don't know the whole code by heart, so to understand what you
speak about, we would have to read the code you speak about carefully;
and even so, when I see the kind of changes you propose, I'm not sure
we will just say that's good ideas out of our head by just reading
code. You seem to be proposing mostly API change or code optimization.
But as often in optimization, it starts with gut feeling (except when
dealing with obvious bad designs), and some algorithm cost
computation, but in the end only real testing will really tell.
So if you really feel that's the way to go, you can still implement
it, test it, and if it appears to be a lot better than previously,
then you won. Propose a patch with some benchmark results and someone
will have at look at this.

Now this said, I really wonder if API changes or algorithm
optimizations are the best way to start in OpenSource contribution. A
codebase like GIMP is huge and very complicated and you want to start
with base classes. First of all, classes which are used in a lot of
places may also break many different pieces of code if you change
things (API or algorithm) there. So that implies a lot of regression
testing, which means a lot of time.
Second, even though base classes are indeed used in a lot of places,
and optimizations are always good, well it is not that obvious that
the optimization will get that tremendous speed improvements compared
to all the other things done along the way.
Last, API change just for the sake of API change, I'm not sure that's
the best idea. We will usually do something because we actually want
to use it and see it will make actual code better. I'm not sure if API
change which "may" make some future code better is a good way to do
it.

I would think an easier way to start contributing is to fix bugs. We
have quite a lot of bugs in our bug tracker waiting to be fixed. Just
pick some of them, and fix them. Then you are sure this will be wanted
code, and there is no "maybe" or incertitude. Also that's a lot
easier, though very visible.

But if you're sure your propositions are worth it, the best is to do
the changes and propose patches. :-) As I said, I haven't looked at
them in details. Maybe that's great ideas, no idea. I know some
contributors start with base consolidations, not fixes. It happens.
In any case, have fun with GIMP,

Jehan


1. gimp/libgimpmath/gimpmathtypes.h (file in
question:gimp/libgimpmath/gimpmatrix.h(c))
This file declares math structures that gimp uses like vectors and
matrices. The GimpMatrix structure come in 2X2, 3X3 and even 4X4
versions.
Each matrix is a 2Dimensional gdouble array with the appropriate amount
of
elements to span the NXN matrix.I believe this data structure is used
for
computation during image editing. There are functions handling
comparisons, identities, transformations, rotations, translations and
various other
matrix operations. Possible changes: I believe the declaration of 3
special
kinds of gimp
matrices can be generalized to a struct (or class) that holds and
defines
an NXN matrix. We
could make it as general as possible to save the amount of code
necessary
to complete the tasks. This also eliminates two extra structs in the .h
file. We could also change the structure that holds the matrix elements.
One way could be by making a nested linked list to emulate an NXN
matrix.
This way, we keep everything in memory and not on the stack. If
necessary,
we could even overload the [] operator to make the functionality act
like
an array. We could also use the std::vector<T> data structures included
in
the <vector> library to allow for pushing and popping of matrix data
structures to make them dynamic and or more fail-safe.

2. gimp/app/core/gimpcontainer.h
This class contains a data structure that is used to store different
things
about the
various objects in gimp. It works hand and hand with the GimpObject
class.
This
class uses what I believe to be some form of tree or heap structure. The
class
refers to add, remove, reorder, and getChild functions that are defined
across the
class. The gimp.h code uses the GimpContainer class pointers for
everything
from fonts, to documents, to displays. As this data structure is used
with
GimpObject (which controls a large amount of functionality in gimp) and
is
heavily
referenced in the gimp.h file, optimizing this class could go a long way
in
optimizing the code. If we decrease the amount of time to “reorder” the
tree, then
we decrease the amount of time several other objects take to be
initialized
and
added to the tree.

3. gimp/libgimpmath/gimpvector.h(c)
The GimpVector data structure keeps track of axis orientations and
lengths.
I believe this is used in the various drawing tools. I also believe the
automated shapes functions may use it for drawing polygons. The vector
data
structure is a structure that holds four gdouble variables that are
separately declared (gdouble x, y, z, w for the 4axis vector for
example).
There are three
versions of the gimp vector: 2axis, 3axis, and 4axis. A potential change
to
GimpVector could be altering the way that it is stored like we plan to
change the GimpMatrix. This means making a
streamlined generalized vector that can be of dimension N. Storing the
axes
in an std::vector<T> or a linked list of size N could generalize the
vector
to be declared of any arbitrary number of axes. Another thing we could
do
is overload the operators between vectors such as addition, subtraction
and
multiplication. Currently they are of the form, GimpVector
add(GimpVector
&gv1,GimpVector &gv2). We could make it as easy as adding two vectors
with
the + operator to make the code more readable. We can also overload
various
other operators to make the GimpVector data structure more flexible and
powerful. This hopefully will increase the functionality and potency of
the
GimpVector data structures and make them more accessible to new Gimp
developers in the future.
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