This is a planning idea for new PaintCore for GIMP 2.8 or beyond.

1: The "Why?".

Current paint core is just not flexible enough and migration to GEGL based paint core is planned anyway. So why not do the best possible paint core since we are redoing it anyway?

2: What is the goal?

In general: Best possible digital "painting" tools. That should NOT include any natural painting things like watercolor emulation or alike but full featured tool for use on digital medium for image processing, touch-up etc.

What does the above mean? * Easily extensible framework for creation of painting tools * Fully dynamic painting, meaning that every adjustable aspect is user input controllable
* Easily distributable paint tool presets that allow a the complete tool context to be saved and loaded either on same or different machine

How I see that happening?

Step one: Event handler for paint tools.
This is a very important bit for fully featured tools. All devices have some dynamic properties that are useful in painting on the digital canvas. * Mice have velocity(and acceleration), cheap tablets add pressure, more expensive ones may add even more axis. * All movement has direction
* Purely calculated axis like random can be extremely useful. * Paint tools want events at a constant distance or at a constant distance AND rate.
Devices will never provide exactly what is needed so adjustment is required. The extra events need to be discarded and events that are missing interpolated. The method of interpolation depends on the axis in question.

So event handler should: * be able to handle a number of device axis and apply per device curves * support calculated axis based on what device provides and also support applying device curves
* support a dynamic selection of arbitrary purely calculated axis (random, iterator, sin, cos, sawtooth, box); * be able to deliver constant distance and constant rate events

Step two: Paint Core
Paint core should provide framework for interacting with the canvas, controlling the event handler and the saving and loading of paint tool contexts as Paintbrushes, Erasers, Sponges etc with previews. Paint core should also facilitate curves based mapping of event handler axis to tool parameters. All paint tools expose parameters that may be mapped to any axis event handler can provide.
Step X:
Paint tools:
Brush tool: Simple painting tool, support for all current brush formats is a must. Must support at least scaling and rotation of brushes. Airbrush tool: Almost the same as brush tool but orders constant rate of events from event handler.
etc tools: Use paint tool framework, only the paint action itself differs.

That's just my Idea for the step two of my last piece from a while ago on brushes in GIMP.

Sven, Pippin, Peter, everybody - comments?

On Sunday 08 June 2008 03:07:15 David Gowers wrote:

* support a dynamic selection of arbitrary purely calculated axis (random, iterator, sin, cos, sawtooth, box);

A 'Dynamic selection'? what does this mean? Just that you are free to choose one of these?

In my vision you could choose arbitrary number of these including the same item twice and then apply different curves to both instances. I'm not 100% how that can be implemented tho.

* If you treat random, etc as axis, you need to provide a method of scaling them, or can you guarantee that they all range 0 .. 1.0 ?

They would all have range of 0.0...1.0 just like random, velocity etc now in SVN.

I think sin and cos could be implemented as a subcase of 'custom': a custom curve input.

All these calculated axis would be a sort of custom. Allowing a free formula type is an option as well but It may be harder to implement.

* be able to deliver constant distance and constant rate events

You mean events at a constant distance spacing or a constant time spacing?

I mean both. The dream is that paincore would only need to worry about painting a stamp at a given event, the "where?" part is all handled by paint core. The distance in this case is the stamp spacing.

Is there any other way that the 'Use color from gradient' or 'Fade' options could be replicated?

Replicated? It's paint cores job to provide these two features and any other numerically controlled options and possibly expose their control values for event mixed influence.

Theres a check grid now in SVN. In my vision in tool pane each option that supports it has a checkbox to turn dynamics on and off and a button to curves about that specific parameter. Additionally there are sliders for scaling the dynamics as a whole for quick adjustment. If you load a tool the changes made are forgotten. They are just adjustments to the current ie paintbrush, where as changes in curves create and "unsaved" tool that can be marked that way so the user knows that they need to save it either as a new tool or overwriting the parent.

-- Alexia

P.S redirecting back to list,