This script chooses a random wallpaper, resizes it, places the time on it, and displays it on a 320x240 AdaFruit PiTFT for Raspberry Pi using the framebuffer.

show-time.sh

#!/bin/bash

export indir=${HOME}/wallpapers
export infile=`find ${indir} -type f | sort -R | tail -n 1`

export workdir=${HOME}/.wallpaper
export resizedfile=${workdir}/resized.png
export timefile=${workdir}/time.png
export outfile=${workdir}/time-final.png
export time=`date`

export loc=+15+200

mkdir -p ${workdir}

convert -resize 320x240 "${infile}" "${resizedfile}"

convert -size 320x240 xc:lightblue -transparent lightblue -pointsize 20 \
        -stroke black -strokewidth 8 -annotate ${loc} "${time}" -blur 0x8 \
        -fill white   -stroke none   -annotate ${loc} "${time}" \
        "${timefile}"

composite -gravity center "${timefile}" "${resizedfile}" "${outfile}"

sudo fbi -T 2 -d /dev/fb1 -noverbose -a "${outfile}"