slight modification of: https://freakspot.net/en/git-diff-for-images/ requires imv

git-imgdiff

#!/bin/bash
SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
compare $2 $1 png:- | montage -border 2 -bordercolor black -geometry +4+4 $2 - $1 png:- | imv_config="${SCRIPT_DIR}/git-imgdiff-imv-config" gitimgdiff_file="$1" imv -f -d -w $1 -

git-imgdiff-imv-config

[options]
overlay = true
overlay_text = $(echo -e "Filename: ${gitimgdiff_file}\nZoom: ${imv_scale}%")
[binds]
a = exec git add ${gitimgdiff_file}