change-background

#!/bin/bash
#
# A script for changing login/desktop/lockscreen backgrounds

RED="\033[0;31m"
NC="\033[0m" # No Color
XML_FOLDER=/usr/share/images/desktop-base
WIDTH=1920
HEIGHT=1200

## Check if the file exists and whether it's an image
is_image_file() {
    FULL_PATH=$(readlink -f $1)
    if [[ ! $(file -ib $(readlink -f $1)) =~ ^image/ ]]; then
        printf "${RED}Error: Invalid or non-existent image file $FULL_PATH ${NC}\n" &&
            exit 1
    fi
}

## Change desktop background
change_desktop() {
    is_image_file $1
    gsettings set org.gnome.desktop.background picture-uri file://$FULL_PATH
}

## Change login background
change_login() {
    is_image_file $1
    `d}us-launch | sed 's/^/export /'`
    gsettings set org.gnome.desktop.background picture-uri file://$FULL_PATH
}

## Change lockscreen background(needs root access)
change_lockscreen() {
    is_image_file $1
    if [[ $EUID -ne 0 ]]; then
        printf "${RED}Error: Need root access to write to $XML_FOLDER ${NC}\n"
        exit 1
    fi

    XML="<background>
    <static>
        <duration>8640000.0</duration>
        <file>
        <size width=\"1440\" height=\"900\">$FULL_PATH</size>
        </file>
    </static>
</background>"

    XML_PATH=$XML_FOLDER/lockscreen-background.xml

    echo Writing to XML file $XML_PATH...
    echo "$XML" > $XML_PATH

    sleep 1
    echo Symlinking...
    sleep 1
    ln -sf $XML_PATH /etc/alternatives/desktop-background.xml
    echo Done. Restart your window manager for change to take effect
}

USAGE="Usage: change-background {login|lockscreen|desktop} FilePath"

if [[ $# -le 1 ]]; then
    echo $USAGE
    exit
fi

case $1 in
    "login") change_login $2;;
    "desktop") change_desktop $2;;
    "lockscreen") change_lockscreen $2;;
    *) echo Invalid first argument, should be either login, desktop or lockscreen;;
esac