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" (below drawing board or Ctrl+D) 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,
        mostly for mass productions of image files, but most commands 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 brwosing the main menu, a help texts about the
    highlighted item also appears in the status bar. The Menu can completely
    navigated with the keyboard. Just hold Alt and use the direction keys
    (up, down, left and right) or the highlighted letters. When holding the
    Alt key you can also see which Alt + letter combinations trigger which
    button.

  Pendulum
    The first tab contains the settings that define the properties of the
    pendula (X and Y), which move along the x and y axis in a lateral
    manner. On the second Tab are identical controls for the Pendula Z and R
    which together with X and Y determine the shape of the drawing. Z does a
    circling movement, R is a rotation (around Z's axis or origin).

    All controls from top to bottom and left to right are: an on/off switch
    which activates the whole pendulum with all settings. After that follows
    the pendulum's amplitude (here called radius). This determines the size
    in the direction the pendulum moves. Below that follows amplitude
    damping, which reduces the amplitude over time, so that the drawing will
    spiral toward the center. Since this is all computed, time refers to the
    line length. Damping can take place in a steady (minus '-') or in a
    slowing, procentual manner ('*'). The third row is labeled acceleration,
    which refers to an additional dynamic of the amplitude damping.

    The forth row lets you dial in the speed (frequency). This is the most
    fundamental to the shape. For instance 2 means that the pendulum swings
    back and fourth twice as fast. To the right you can choose an additional
    factor the frequency gets multiplied with. This can be a constant like
    Pi or Phi or the frequency of another pendulum or just simply one. This
    is especially handy when browsing the classic shapes with three pendula.
    For these the frequency of X and Y has to be the same - which will be
    ensured when you set the frequency factor of Y to X (or vice versa) and
    keep the frequency of Y to one. The next combo control below adds
    decimals to the frequency value for more complex rotating drawings.
    Behind that are two check boxes to invert the final frequency value to
    1/x or to flip the direction of the pendulum. Below that follows a
    frequency damping, which works the same as the second row only with
    slightly different optical results.

    The last row starts with a slider to fine tune the starting point of the
    pendulum. It can be chosen between zero and a quater rotation. This can
    have great effects on the shape. Because of the special desirability
    offsets of an half (180 degree) or quarter (90 degree) rotation can be
    activated by checkbox (to the right of the slider). The final offset is
    the sum of the checked.

  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 an complete image and
    saving it in an arbitrary named PNG, JPG or SVG file (the file ending
    decides). The submenu above onle set the preferred format, which is the
    format of serial images and the first wild card in dialog. Above that is
    another submenu for setting the image size.

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

SEE ALSO
    App::GUI::Cellgraph

    App::GUI::Dynagraph

AUTHOR
    Herbert Breunung (lichtkind@cpan.org)

COPYRIGHT & LICENSE
    Copyright(c) 2022 by Herbert Breunung

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

