The package bzdev-wallpapers contains a series of image files
containing 'wallpaper' images for use on Debian systems. The images
are based on David Hilbert's space-filling curve, and are intended to
provide a low-key, unobtrusive background that could work well with
Pop!_OS "dark mode", where it can be annoying if the 'wallpaper' is
too bright.  The space filling curve was added to make it easier to
detect the boundaries of a window in cases where it or its contents
(for some reason) match the color of a background.

The images are

   * BZDev-Hilbert_Curve_Dark_Blue-by_Bill_Zaumen.png

   * BZDev-Hilbert_Curve_Gray_Brown-by_Bill_Zaumen.png

and use the same pattern but in different foreground and background
colors (by design these are similar). The naming convention for these
files was based on the pattern used by image files provided by the
packages system76-wallpapers and pop-wallpapers. The background colors
were chosen to match ones used by a couple of files in these two
packages.

The images were generated with the program in the file
HilbertCurve.java (which requires a library that as of June 17, 2020
has not been put on GitHub).  This program is needed to create the
images, but the images are included in this git repository, so the
Java program does not have to be run unless new files are added or the
images were changed (by modifying HilbertCurve.java or its use in
Makefile).  Because it is desirable to be able to build the package
without running Java (due to a library being not yet available), the
image files are included in the git repository.

To build a Debian package,  run

   make package

and everything should happen automatically (one should first change
the VERSION variable in the makefile and change the name of the
package if the Makefile or Java class is modified).

The Other files used are

    * bzdev-wallpapers.xml - an XML file required by gnome defining
      properties for each wallpaper image. This has to be modified if
      additional images are added or if an image is modified and given
      a different name

    * control - the Debian control file.

    * copyright - the standard copyright/license file.

    * changelog - the changelog file.

    * Makefile - in particular, the command-line arguments for
      creating the images are located in this file.

The programs needed to build a package are 'install', gzip, fakeroot,
and dpkg-deb.  The corresponding Debian packages are

    * fakeroot

    * coreutils

    * gzip

    * dpkg

and any packages these require.

To run the Java program, use

   java -p /usr/share/bzdev -m org.bzdev.graphics HilberCurve \
   	FILENAME COLOR LEVEL DEPTH

where
    * FILENAME is the name of the image file to be created. It should
      end with the suffix ".png".

    * COLOR is a hexadecimal number starting with '0x' and followed by
      6 hexadecimal digits, 2 each for the red, green, and blue color
      components in that order.

    * LEVEL is used to get the foreground color from the background
      color. It is the number of times the method brighter() is called
      on a color whose initial value is the background color when
      LEVEL is positive and its absolute value the number of time the
      method darker() is called on a color whose initial value is the
      background color when the value of LEVEL is negative.

    * DEPTH is a limit on the number of recursive calls used when
      generating the curve.  A good value is '6'.

Because gnome window managers seem to leave bar at the top and this
bar covers part of the image, some extra width is allowed at the top
of the image before the curve starts.