Generate random p4m tile backgrounds with ImageMagick and feh.

backgroundTile.sh

#!/bin/bash

################################################################################
#                                   About
################################################################################
#
# Dumb script to generate a random 100x100 tile in the p4m background group.
# Uses 'feh' to tile the image as a desktop background.
#
# Install to crontab -e to rengerate at a fixed interval. E.g. every 5 min:
#  */5 * * * * /home/youruser/bin/someplace/you/put/this/script.sh
#
# Credit goes primarily to the docs, I haven't deviated much:
#   http://www.imagemagick.org/Usage/canvas/#tile_diagonal
# From there it was just a matter of tweaking params wildly until the desired
# effects are obtained. Yay art.
#
# For big smooshy looking plasma effects try a larger tile size (e.g. 200x200)
# and a higher blur (e.g. 0x10). Set GRAYSCALE=1 if you find the colours bright
# and distracting.
#
# - Daniel McCarney - [email protected]
################################################################################

################################################################################
#                             Tile Gen Params
################################################################################

# Size of each indidivual tile ( widthxheight in pixels )
TILE_SIZE=100x100

# Amount of blur to apply
BLUR=0x4

# Brightness and contrast. Negative to reduce, positive to increase.
BRIGHTNESS=-10
CONTRAST=-30

# If 1, output in grayscale. Otherwise map to RGB
GRAYSCALE=0

################################################################################

TMP_FILE=$(mktemp --suffix='.jpg')
if [ $? -ne 0 ]; then
  echo "Error: unable to create temp file. Is 'mktemp' working?"
  exit 1
fi

if ! type "convert" &> /dev/null; then
  echo "Error: You must install ImageMagick and have 'convert' on your \$PATH."
  exit 1
fi

if ! type "feh" &> /dev/null; then
  echo "Error: You must install feh and have it on your \$PATH."
  exit 1
fi

if [ $GRAYSCALE -ne 0 ]; then
  OUTPUT_COLOURSPACE=gray
else
  OUTPUT_COLOURSPACE=RGB
fi

convert -size $TILE_SIZE xc: +noise Random   \( +clone -transpose \) \
        \( +clone -sparse-color voronoi '%w,0 blue 0,%h red' \) \
        -composite \
        \( +clone -rotate -90 \) +append \
        \( +clone -rotate 180 \) -append \
        \
        -virtual-pixel Tile -blur $BLUR -auto-level \
        -separate -background white \
        -compose ModulusAdd -flatten -channel R -combine +channel \
        -set colorspace HSB -colorspace $OUTPUT_COLOURSPACE \
        -brightness-contrast $BRIGHTNESSx$CONTRAST $TMP_FILE

export DISPLAY=:0         #Feh gets mad in a cronjob if it doesn't know the DISPLAY
feh --bg-tile $TMP_FILE
rm $TMP_FILE