lsix: like 'ls' but shows images within a terminal using SIXEL graphics

lsix

#!/bin/bash

# lsix: like ls, but for images.
# Shows thumbnails of images with titles directly in terminal. 

# Version 1.0
# hackerb9, June 2017


numcolors=16   # Number of colors in the palette, if TERM is not xterm

cleanup() {
    echo $'\e\\'		# Escape sequence to stop SIXEL
    exit 0
}
trap cleanup SIGINT SIGHUP SIGABRT


if [[ "$TERM" =~ xterm ]]; then
    # Attempt to set the number of colors to 1024.
    # This will work for xterm, but fail on a real vt340.
    IFS=";"  read -a REPLY -s -t 0.1 -d "S" -p $'\e[?1;3;1024S'
    [[ ${REPLY[1]} == "0" ]] && numcolors=${REPLY[2]}
fi

if [[ $# == 0 ]]; then
    # No command line args? Use a sorted list of image files in CWD
   shopt -s nullglob nocaseglob
   set - *{jpg,jpeg,png,gif,tiff,tif,p?m,x[pb]m,bmp,ico,svg,eps}
   [[ $# != 0 ]] || exit
   mapfile -t < <(printf "%s\n" "$@" | sort) 
   set - "${MAPFILE[@]}"
fi

if [[ $# -le 21 ]]; then 
    # Only a few pictures to show, do it in one chunk.
    montage -tile 7x1 -label %f -background black -fill white "$@" gif:- \
	| convert - -colors $numcolors sixel:-
else
    # Lots of pictures, so show them a row at a time instead
    # of taking a long time to make one huge montage.
    while [ $# -gt 0 ]; do
	while [ $# -gt 0 -a  ${#onerow[@]} -lt 7 ]; do
	    len=${#onerow[@]}
	    onerow[$len]="$1"
	    shift
	done
	montage -tile 7x1 -label %f \
		-background black -fill white \
		"${onerow[@]}" gif:-  \
	    | convert - -colors $numcolors sixel:-
	onerow=()
    done
fi    
    
######################################################################
# NOTES:

# * Usage: lsix [ FILES ... ] 
# * FILES can be any image file that ImageMagick can handle.
# * If no FILES are specified the most common file extensions are used.
# * Non-bitmap graphics often work fine (.svg, .eps, .pdf, .xcf).
# * Because this uses escape sequences, it works seamlessly through ssh.
# * Only dependency is ImageMagick (apt-get install imagemagick).

# Your terminal must support SIXEL graphics. E.g.,
#
#     xterm -ti vt340

# * To make vt340 be the default xterm type, set this in .Xresources:
#
#     ! Allow sixel graphics. (Try: "convert -colors 16 foo.jpg sixel:-").
#     xterm*decTerminalID	:	vt340

# * Be cautious using lsix on videos (lsix *.avi) as ImageMagick will
#   try to make a montage of every single frame and likely exhaust
#   your memory and/or your patience.

# BUGS

# * Directories are not handled nicely.