NAME
    App::GUI::Harmonograph - sculpting beautiful circular drawings

SYNOPSIS
    1.  start the program (harmonograph)

    2.  read this POD or check dialogs from help menu

    3.  move knobs and observe how preview sketch reacts til you got an
        interesting configuration

    4.  push "Draw" (Ctrl+D or below drawing board) to produce full image

    5.  choose "Save" in Image menu (or Ctrl+S) to store image in a PNG /
        JPEG / SVG file

    6.  choose "Write" in settings menu (Ctrl+W) to save settings into an
        INI file for tweaking them later

    Please note that quick preview gets only triggered by the pendulum
    controls (section X, Y Z and R).

    After first use of the program, a config file .harmonograph will be
    created in you home directory. You may move it into "Documents" or your
    local directory you start the app from.

DESCRIPTION
    An Harmonograph is an apparatus with several connected pendula, creating
    together spiraling pictures :

    This is a cybernetic recreation of an Prof. Blackburns invention with
    several enhancements:

    *   third pendulum can rotate

    *   pendula can oscillate at none integer frequencies

    *   changeable amplitude and damping

    *   changeable dot density and dot size

    *   3 types of color changes with changeable speed and polynomial
        dynamics

Mechanics
    The classic Harmonograph is sturdy metal rack which does not move while
    3 pendula swing independently. Let us call the first pendulum X, because
    it only moves along the x-axis (left to right and back). In the same
    fashion the second (Y) only moves up and down. When both are connected
    to a pen, we get a combination of both movements. As long as X and Y
    swing at the same speed, the result is a diagonal line. Because when X
    goes right Y goes up and vice versa. But if we start one pendulum at the
    center and the other at the upmost position we get a circle. In other
    words: we added an offset of 90 degrees to Y (or X). Our third pendulum
    Z moves the paper and does exactly the already described circular
    movement without rotating around its center. If both circular movements
    (of X, Y and Z) are concurrent - the pen just stays at one point, If
    both are countercurrent - we get a circle. Interesting things start to
    happen, if we alter the speed of of X, Y and Z. Than famous harmonic
    pattern appear. And for even more complex drawings I added R, which is
    not really a pendulum, but an additional rotary movement of Z around its
    center. The pendula out of metal do of course fizzle out with time,
    which you can see in the drawing, in a spiraling movement toward the
    center. We emulate this with a damping factor.

GUI
    The general layout of the program has three parts, which flow from the
    position of the drawing board.

    1   In the left upper corner is the drawing board - showing the result
        of the Harmonograph.

    2   The whole right half of the window contains the settings, which
        guide the drawing operation. These are divided into two tabs -
        roughly devided in form and decoration.

    3   The lower left side contains buttons which are a few commands, but
        most are in the main menu.

    Please mind the tool tips - short help texts which appear if the mouse
    stands still over a button or slider. Also helpful are messages in the
    status bar at the bottom: on left regarding images and right about
    settings. When holting the Alt key you can see which Alt + letter
    combinations trigger which button.

  Pendulum
    The content of the first tab are the settings that define the properties
    of the 4 pendula (X, Y, Z and R), which determine the shape of the
    drawing. X moves the pen left - right (on the x axis), Y moves up -
    down, Z does a circling movement, R is a rotation ( around Z's axis).
    Each pendulum has the same three rows of controls.

    The first row contains from left to ritght an on/off switch. After that
    follows the pendulum's amplitude and damping. Amplitudes define the size
    of the drawing and damping just means: the drawings will spiral toward
    the center with time (line length).

    The second row lets you dial in the speed (frequency). For instance 2
    means that the pendulum swings back and fourt twice as fast. The second
    combo control adds decimals for more complex drawings.

    The third row has switches to invert (1/x) frequency or direction and
    can also change the starting position. 2 = 180 degree offset, 4 = 90
    degree (both can be combined). The last slider adds an additional fine
    tuned offset between 0 and 90 degree.

  Line
    The second tab on the right side has knobs that set the properties of
    the pen. First how many rotations will be drawn. Secondly the distance
    between dots. Greater distances, together with color changes, help to
    clearify muddled up drawings. The third selector sets the dot size in
    pixel.

  Colors
    Below that on the second tab are the options for colorization and this
    has in itself three parts. Topmost are the settings for the color
    change, which is set on default to "no". In that case only the start
    (upper) color (below the color change section) will be used, and not the
    end (target) color (which is even below that).

    Both colors can be changed via controls for the red, green and blue
    value (see labels "R", "G" and "B" ) or hue, saturation and lightness
    (HSL). The result can be seen in the color monitor at the center of a
    color browser.

    An one time or alternating gradient between both colors with different
    dynamics (first in second row) can be employed. Circular gradients
    travel around the rainbow through a complement color with saturation and
    lightness of the target settings. Steps size refers always to how maby
    circles are draw before the color changes.

    The third part on the second tab grants you access to the color store of
    config file .harmonograph. There you can store your favorite colors
    under a name and reload or delet them later. The upper row is for
    interactions with the sart color and the lower with the end color.

  Commands
    In the lower left corner are two rows of command buttons. All other
    commands are in the menu.

    The upper row has only one button for making a full drawing. This might
    take some time if line length and dot density are high. For that reason
    - changes on the pendulum settings (first tab) (and only these) produce
    an immediate drawing to better understand the nature of your changes. In
    the interest of time, these are only sketches. For a full drawing that
    takes all settings into account you need to push the "Draw" button or
    Press Ctrl + D.

    The second row has commands to quickly save many files. First push "Dir"
    to select the directory and then type directly into the secand text fiel
    the file base name - the index is found automatically. Every time you
    now press "Save" a file with the current image is saved under the path:
    dir + base name + index + ending (set in config). The index
    automatically autoincrements when changing the settings. Push "INI" next
    to it to also save the settings of the current state under same file
    name, but with the ending .ini.

  Menu
    The upmost menu bar has only three very simple menus. Please not that
    each menu shows which key combination triggers the same command and
    while hovering over an menu item you see a short help text the left
    status bar field.

    The first menu is for loading and storing setting files with arbitrary
    names. Also a sub menu allows a quick load of the recently used files.
    The first entry lets you reset the whole program to the starting state
    and the last is just to exit (safely with saving the configs).

    The second menu has only two commands for drawing and saving an complete
    image in an arbitrary named PNG, JPG or SVG file (the file ending
    decides).

    The third menu has some dialogs with documentation and additional
    information.

AUTHOR
    Herbert Breunung (lichtkind@cpan.org)

COPYRIGHT
    Copyright(c) 2022 by Herbert Breunung

    All rights reserved. This program is free software and can be used and
    distributed under the GPL 3 licence.

