package ifs-fractals

1.2.0 (2026-08-23)

• API documentation, published at https://ocaml.org/p/ifs-fractals and built locally with dune build @doc. The library has an interface file, lib/ifs_fractals.mli, in which every type, function and predefined fractal carries a documentation comment, and doc/index.mld is the landing page of the package. The interface also settles what the library actually offers: the plumbing of the PNG writer (output_png, add_chunk, crc_table, encode, ramp_color) and of the Fractint reader (words, group_entries, thresholds, cumulate, ...) is no longer exported, along with select_image, pixel_of_point, accumulate and viewport. Everything the command and the documented API use is unchanged.
• Fixed: sierpinski drew an empty window and koch a speck in the middle of one. Both had their coefficients written in the order of a Fractint table — a b c d e f for x' = a*x + b*y + e — rather than the order of kf, so neither described the fractal it was named after, and neither landed in the region its record asked to display. The transforms are reordered and both viewports now frame the attractor: sierpinski is the triangle on (0,0), (2,0), (1, √3), and koch the curve from (0,0) to (1,0). This had been the case since the first commit, in 2010.
• A test suite, run with dune test: the affine maps and the projection, the chaos game, the framing of an attractor, the Fractint parser and the errors it reports, and the PNG writer, whose output is decoded and checked rather than counted in bytes. It needs no display and no new dependency.
• The predefined fractals moved out of lib/ifs_fractals.ml into their own lib/fractals.ml, together with the point, transfo and ifs types, so that adding or tuning a fractal no longer touches the code that draws it. Ifs_fractals re-exports them, so the library API is unchanged, and so is the toplevel workflow (the loader now uses #mod_use for the new file).
• show fs n draws a fractal, waits for a keypress and closes the window. Unlike draw, it leaves the program inside an event call, which is what lets the window manager's close button work.
• Fixed: after the graphics window was closed — by Graphics.close_graph or by the window manager — draw failed with Graphic_failure "graphic screen not opened" instead of opening a new window. window_open is now a function that asks the graphics library rather than a stale flag.
• Fractals can be read from Fractint .ifs files: ifs-fractals -f FILE.ifs NAME from the command line, load_fractint from the library. The format's plain weights are converted to cumulative thresholds (or derived from each map's determinant when the file gives none), and the viewport, which the format does not record, is fitted to the attractor by fit. example/classics.ifs collects a dozen classic systems to try it on.
• Three-dimensional systems — Fractint's (3D) entries, twelve or thirteen numbers per transform — are read and drawn as well, projected orthographically from a direction given by -v YAW,PITCH in degrees (?yaw and ?pitch in the library). Reading a file now returns a system, either Flat of ifs or Solid of ifs3; draw_system, show_system and save_png_system take either.

1.1.0 (2026-08-05)

• Fractals can now be rendered to PNG files without a graphical display: ifs-fractals -o fern.png barnsley from the command line (with an optional -s WIDTHxHEIGHT), or save_png from the library. The PNG writer is self-contained — no new dependency.
• Density coloring: with -c (or save_png ~color:true), pixels are colored by how often the chaos game visits them, on a log scale from light green to dark blue.

1.0.0 (2026-07-27)

First release on opam, sixteen years after the first commit.

• Packaged with dune: the code now builds as a library (ifs-fractals, module Ifs_fractals) and an ifs-fractals command-line executable.
• The historical toplevel workflow (#use "ifs_fractals.ml";;) still works from a clone of the repository.
• Sixteen predefined fractals, including the five added in 2026: maple, fiddlehead, vegvisir, sunflower and lace.