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    1 IfsCompose
    2 ----------
    3 
    4 IfsCompose is a plug-in for GIMP that allows
    5 the creation of Iterated Function System fractals by direct
    6 manipulation onscreen of the component transforms.
    7 
    8 
    9 IFS Fractals
   10 ------------
   11 
   12 You may be familiar with IFS's from the screen
   13 hack 'Flame'. They are also the basis of fractal image compression.
   14 
   15 For a brief introduction to IFS's see Foley and van Dam, et
   16 al,. _Computer Graphics, Principles and Practice_, 2nd Ed., 
   17 (Addison Wesley, 1990).
   18 
   19 The standard references in the field are Michael Barnsley's books (though
   20 I haven't looked at them yet):
   21 
   22 M. Barnsley, _Fractals Everywhere_, Academic Press Inc., 1988.
   23 M. Barnsley and L. Hurd, _Fractal Image Compression_, Jones and
   24 Bartlett.
   25 
   26 Briefly, you take a point and repeatedly apply one of a set of
   27 transformations to it, choosing randomly between them, and plot the
   28 point at each step. An interesting result (the Collage Theorem) says
   29 that if you can find a set of transformations that break up an image
   30 into smaller copies of itself, then the resulting fractal exactly
   31 reproduces the original image.  For example, here is a classic image
   32 of a leaf and the same image with the four component transforms
   33 colored distinctively.
   34 
   35 But the best way to appreciate this may to install this program and
   36 try it out. I've extended the basic concept as found in
   37 Foley and van Dam to include transformations in color space as
   38 well as in real space.
   39 
   40 Installation
   41 ------------
   42 The included Makefile should work with minor modifications on most
   43 systems if you have installed Gimp normally. Put the resulting binary
   44 in ~/.gimp/plug-ins or the system-wide plug-ins directory.
   45 
   46 The included files gtkaspectframe.c/.h implement a modified frame
   47 widget that guarantees that the aspect ratio of the child widget
   48 remains constant when the parent is resized. It's sort of specialized,
   49 but if you think it would be useful for other purposes, let me know
   50 and I'll lobby for its inclusion in the standard gtk.
   51 
   52 Use
   53 ---
   54 The interface is somewhat complex and it may take you a little while
   55 to get the hang of it. (There are 19 parameters for each
   56 transformation in your fractal, after all). The best way to learn is
   57 probably to start by making small changes, and seeing what they
   58 do. Click on the transformations (represented by polygons) in the
   59 design window to manipulate them interactively.
   60 
   61 Button-1: rotate/scale
   62 Button-2: distort
   63 Button-3: move
   64 
   65 If you hold down shift while clicking, you can select multiple polygons
   66 to apply the transformation to.
   67 
   68 Try not to click too near the center of a polygon, as this will
   69 amplify your actions.
   70 
   71 Note that if you render onto an image with an alpha channel, the
   72 background will be transparent (very useful for compositing several
   73 fractals), otherwise the background will be the current background.
   74 
   75 There are tutorials and some example images at:
   76 
   77  http://www.gtk.org/~otaylor/IfsCompose/ifs_tutorial/tutorial.html
   78  http://tigert.gimp.org/gimp/ifs-compose/
   79 
   80 
   81 Have fun!
   82 
   83 Owen Taylor