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IfsCompose ---------- IfsCompose is a plug-in for GIMP that allows the creation of Iterated Function System fractals by direct manipulation onscreen of the component transforms. IFS Fractals ------------ You may be familiar with IFS's from the screen hack 'Flame'. They are also the basis of fractal image compression. For a brief introduction to IFS's see Foley and van Dam, et al,. _Computer Graphics, Principles and Practice_, 2nd Ed., (Addison Wesley, 1990). The standard references in the field are Michael Barnsley's books (though I haven't looked at them yet): M. Barnsley, _Fractals Everywhere_, Academic Press Inc., 1988. M. Barnsley and L. Hurd, _Fractal Image Compression_, Jones and Bartlett. Briefly, you take a point and repeatedly apply one of a set of transformations to it, choosing randomly between them, and plot the point at each step. An interesting result (the Collage Theorem) says that if you can find a set of transformations that break up an image into smaller copies of itself, then the resulting fractal exactly reproduces the original image. For example, here is a classic image of a leaf and the same image with the four component transforms colored distinctively. But the best way to appreciate this may to install this program and try it out. I've extended the basic concept as found in Foley and van Dam to include transformations in color space as well as in real space. Installation ------------ The included Makefile should work with minor modifications on most systems if you have installed Gimp normally. Put the resulting binary in ~/.gimp/plug-ins or the system-wide plug-ins directory. The included files gtkaspectframe.c/.h implement a modified frame widget that guarantees that the aspect ratio of the child widget remains constant when the parent is resized. It's sort of specialized, but if you think it would be useful for other purposes, let me know and I'll lobby for its inclusion in the standard gtk. Use --- The interface is somewhat complex and it may take you a little while to get the hang of it. (There are 19 parameters for each transformation in your fractal, after all). The best way to learn is probably to start by making small changes, and seeing what they do. Click on the transformations (represented by polygons) in the design window to manipulate them interactively. Button-1: rotate/scale Button-2: distort Button-3: move If you hold down shift while clicking, you can select multiple polygons to apply the transformation to. Try not to click too near the center of a polygon, as this will amplify your actions. Note that if you render onto an image with an alpha channel, the background will be transparent (very useful for compositing several fractals), otherwise the background will be the current background. There are tutorials and some example images at: http://www.gtk.org/~otaylor/IfsCompose/ifs_tutorial/tutorial.html http://tigert.gimp.org/gimp/ifs-compose/ Have fun! Owen Taylor