A tiny script to set the transparency for X windows. If AUTOMAGIC_MODE is "true", it tries to find all gnome-terminal windows and applies the transparency to all of them.

set_gnome-terminal_transparency.sh

#!/bin/bash
# vim: set sts=4 sw=4 et tw=0 :
#
# License: BSD

AUTOMAGIC_MODE="true"
OPACITY_100="0xffffffff"
OPACITY_0="0x0"

: ${XWININFO:=$(type -P xwininfo)}
[[ -z ${XWININFO} ]] && { echo "You need to install xwininfo"; exit 1; }
: ${XPROP:=$(type -P xprop)}
[[ -z ${XPROP} ]] && { echo "You need to install xprop"; exit 1; }

TRANSPARENCY_PERCENT=$1
[[ -z "${TRANSPARENCY_PERCENT}" ]] && { echo "Usage: $0 <transparency in percentage>"; exit 1; }

if [[ ${AUTOMAGIC_MODE} != true ]]; then
    echo "Click on a terminal window to set its transparency as specified (${TRANSPARENCY_PERCENT}%)"
    TERMINAL_WINDOW_XID=$("$XWININFO" | sed -n 's/.*Window id: \([0-9a-fx]\+\).*/\1/p')
else
    # This is very fragile
    TERMINAL_WINDOW_XID=$("$XWININFO" -root -tree | grep -v "Terminal" | sed -n 's/^[[:space:]]\+\([0-9a-fx]\+\).*gnome-terminal.*/\1/p')
fi

if [[ $TRANSPARENCY_PERCENT = 100 ]]; then
    TRANSPARENCY_HEX="$OPACITY_100"
elif [[ $TRANSPARENCY_PERCENT = 0 ]]; then
    TRANSPARENCY_HEX="$OPACITY_0"
else
    TRANSPARENCY_HEX=$(printf "0x%x" $((($(printf "%d" $OPACITY_100) * $TRANSPARENCY_PERCENT)/100)))
fi

echo "Setting transparency to $TRANSPARENCY_HEX (${TRANSPARENCY_PERCENT}%)"
for each in $TERMINAL_WINDOW_XID; do
    "$XPROP" -id $each -f _NET_WM_WINDOW_OPACITY 32c -set _NET_WM_WINDOW_OPACITY $TRANSPARENCY_HEX
done

Hi !

This is awesome but I'm trying to apply it automatically everytime I launch a new gnome-terminal instance.
I've tried putting sh ~/Documents/yourScript.sh in my .zshrc but this way doesn't seems to work (automagic is enabled of course). The transparency will not be applied to the current terminal but to all the other instances.

Do you have a solution ?

Doesn't work for me with

# GNOME Terminal 3.30.2 using VTE 0.54.2 +GNUTLS
gnome-terminal-fedora on Manjaro

change type -P xprop to type xprop & change type -P xwininfo to type xwininfo.

And it does not work.

Pity that this is not as a repo. so we can contribute.
So far, found not working well on byobu, two display scenario. my fix:
only grep those begin with first 5 space, not other like 7 or whatever so don't care the child windows. Also byobu will work as well.
TERMINAL_WINDOW_XID=$("$XWININFO" -root -tree | grep -E -v "Terminal|Gnome-terminal-server" | sed -n 's/^[[:space:]]{5}([0-9a-fx]+).gnome-terminal./\1/p')