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List:       kde-kimageshop
Subject:    canvas widget
From:       Andrew Richards <physajr () phys ! canterbury ! ac ! nz>
Date:       1999-08-02 11:19:47
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Hi folks,

I have (somewhat reticently) uploaded the canvas widget I have been working on
in my spare time.

The files are in the CVS under koffice/kimageshop/canvas and contain a test
Makefile and program which demonstrates some of the features of the widget.

DISCLAIMERS
 - It is work in progress
 - You *will* have to modify the local Makefile to get it to work for you
   no autoconf yet
 - Painting into a layer with an alpha channel is broken
 - The "test images" will be replaced in the future (at the moment they have
   some useful features (other than visual appeal))
 - The classes are not tidy - I haven't decided what needs to be
   public/protected etc.
 - I have been learning a lot about the best way of implementing memory
   management and packing and I expect to rewrite most of this code in the
   near future.
 - Lots of optimizations are possible but I am holding off doing these
   (especially the case based ones) until I decide on a final implementation.
   So don't panic about speed.
 - I WILL tidy it up and the API will change (the basics should stay the same
   though)

No frills test program
 - layers can be selected and turned on and off via the layerlist
   (anyone want to make a nice layer dialog with the relevant signals and
   slots? Also need better eye and link icons)
 - dragging in the image will drag the selected layer
 - Ctrl-clicking in the image will paint into the current layer

A lot of stuff has been designed but not implemented yet - other colour
spaces, zooming, faster repainting, various caching schemes.

Fast Visual
  Check out canvas::setUpVisual() and change the "if (false" to "if (true"
  to see if you can use my fast version of convertFromImage(...) (called
  canvas::convertImageToPixmap(...). On my machine I get a speedup of 2x
  (wrt QT's version) for 32bpp and 3x for 16bpp (Linux intel). This might
  crap out if your machine has a different endianness. Play and code.

Planned changes
 - At the moment the canvas class is a qwidget. I plan to make another class 
   canvasView which handles the display of the widget. That way we can have
   multiple views of the same canvas

What we need
 - Toolbar (signals, slots, blah blah blah)
 - Palettes - brushes, colour, layer
 - Style (copy the good, ditch the bad and invent some thing stylish and new)

I'd like the toolbar and palettes to be based on a palettes class so it can
have a thinner title bar and do nice things like hiding at appropriate
times. Screen real estate is vital in image processing programs so try
not to waste space.

I suggest using QImage as an internal image format until the canvas
stuff settles down (yes, that means RGBA for the moment).


Enjoy,

Andrew Richards
A.Richards@phys.canterbury.ac.nz

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