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283
sixcat
Executable file
283
sixcat
Executable file
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#!/bin/bash
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# sixcat: Use sixel graphics to show an image inside a terminal.
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# sixgif: Use sixel graphics to play an animation inside a terminal.
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# Version 1.0
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# hackerb9, June 2017
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# Sixel graphics are supported by terminals such as the DEC VT340 and
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# emulators, such as 'xterm -ti vt340'.
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# ImageMagick is required. (apt-get install imagemagick)
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# The heart of this program is really just one line:
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#
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# convert foo.jpg sixel:-
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#
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# All the other lines are bells and whistles, mostly to make the image
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# look better by increasing the number of colors available.
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######################################################################
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# Configuration
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######################################################################
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# Number of colors in the terminal's sixel palette.
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# (But also see the -x and -n options).
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default_numcolors=16 # Genuine vt340's had a 16-color palette.
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# Maximum image size is terminal dependent, so we have to guess.
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geometry="-geometry 800x480>" # this was the actual vt340 resolution
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#geometry="-geometry 800x800>" # allows for portrait orientation
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#geometry="-geometry 1000x1000>" # maximum allowed in xterm322
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# Should ImageMagick dither the image to make it look better?
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# (Use dither="" to disable.)
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dither="-dither floyd-steinberg"
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# Maximum number of seconds to wait for a response from the terminal
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# after a color escape sequence request. Usually, terminals respond
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# much faster than 0.1 seconds, but I could imagine it needing to be
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# increased for slow links (e.g., RS232C).
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timeout=0.1
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######################################################################
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# Helper functions
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######################################################################
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usage() {
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cat <<EOF
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Usage: $(basename $0) [-x|-X|-n INTEGER] <imagefiles...>
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-x: Force the use of xterm escape sequences to detect and
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change the palette size instead of defaulting to $default_numcolors.
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If the palette is smaller than 1024, it is set to 1024.
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Note that -x is the default if \$TERM is "xterm".
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-X: Just assume palette size is $default_numcolors.
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Does not use xterm escape sequences regardless of \$TERM.
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-n INTEGER:
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Assume pallete size is INTEGER.
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Does not use xterm escape sequences regardless of \$TERM.
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Note: if this program is called sixgif, it will play GIF animations
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in the top left instead of scrolling all the frames as multiple images.
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EOF
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}
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# Some functions to deal with checking and changing the number of
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# colors the terminal can show. Likely xterm specific, but YMMV.
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getnumcolors() {
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# Query xterm for the palette size and print it.
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# (Negative numbers indicate errors.)
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colors 1 0
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}
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resetnumcolors() {
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# Reset xterm back to its default number of colors.
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# Print the new number of colors (negative if an error occurred.)
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colors 2 0
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}
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setnumcolors() {
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# Request xterm to change the number of colors in its palette.
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# Print the new number of colors (negative if an error occurred.)
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colors 3 $1
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}
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colors() {
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# Send an xterm escape code request in the form: ^[[?1;3;1024S
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# Print the response value (or a negative number if an error occurs)
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csi=$'\e['
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action=$1 # Action. 1 to get, 2 to reset, 3 to set
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value=$2 # Number of colors to set
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returnvalue=-1
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# Raw response is in the same form as request: ^[[?1;0;1024S
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# Let's parse it to be more manageable.
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IFS=";" \
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read -a REPLY -s -t $timeout -d "S" \
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-p "${csi}?1;${action};${value}S"
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if [[ $? != 0 || ${#REPLY} == 0 ]]; then
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# No response to VT escape sequence. Maybe you are not an xterm?
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# Or, perhaps timeout is too short?
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returnvalue=-2
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elif [[ "${REPLY[1]}" == "3" ]]; then
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# Response code 3 means error. Likely too many colors requested.
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returnvalue=-3
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elif [[ "${REPLY[1]}" == "0" ]] ; then
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# 0 means okay. Yay!
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returnvalue=${REPLY[2]}
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else
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# If we get here, response was not in the format we expected.
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# Perhaps user typed during xterm response? Or cosmic rays?
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returnvalue=-4
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fi
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echo $returnvalue
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}
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waitforterminal() {
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# Send an escape sequence and wait for a response from the terminal.
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# This routine will let us know when an image transfer has finished
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# and it's okay to send escape sequences that request results.
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# (E.g., if we want to run resetnumcolors at the end of the program.)
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# WARNING. While this should work with any terminal, if it fails,
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# it'll end up waiting for approximately *forever* (i.e., 60 seconds).
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read -s -t 60 -d "c" -p $'\e[c'
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}
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debugeta() {
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# Given a number of bytes, estimate the amount of time its going
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# to take to send at the current TTY baud rate.
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# Mostly for larks as this will be completely bogus on terminal emulators.
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len=$1
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# Static variables to store TTY type and STTY speed.
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[[ "$TTY" ]] || TTY=$(tty)
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[[ "$SPEED" ]] || SPEED=$(stty speed) || SPEED=0
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echo "sixel command length is $len bytes"
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if [[ "$SPEED" -gt 0 ]]; then
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if [[ "$TTY" =~ /pt || "$TTY" =~ ttyp ]]; then
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echo "pseudoterminal detected (speed estimates only valid for real hardware)"
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fi
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echo "terminal speed is $SPEED bps"
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echo "estimated time to send: $((len*8/SPEED)) seconds"
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fi
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}
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# If the user hits ^C, we don't want them stuck in SIXEL mode
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cleanup() {
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echo -n $'\e[?80h' # Reenable sixel scrolling
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echo -n $'\e\\' # Escape sequence to stop SIXEL
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exit 0
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}
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trap cleanup SIGINT SIGHUP SIGABRT
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######################################################################
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# MAIN BEGINS HERE
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######################################################################
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if [ $# -eq 0 ]; then
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usage
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exit 1
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else
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case "$1" in
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-n|--num-colors) shift
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nflag="$1"
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shift
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# Just assume the palette is n colors. Do not bother checking or changing.
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# (Might be needed for some terminal emulators. I do not know.)
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if [[ "$nflag" -gt 0 ]]; then
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default_numcolors=$nflag
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else
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usage
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exit 1
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fi
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;;
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-x|--force-xterm-colors) shift
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# Force xterm palette manipulation, regardless of $TERM
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# (Might be needed for some terminal emulators. I do not know.)
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xflag=yup
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;;
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-X|--disable-xterm-colors) shift
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# Disable xterm palette manipulation, regardless of $TERM
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# (Might be needed for some terminal emulators. I do not know.)
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Xflag=yup
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;;
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-*)
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usage
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exit 1
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;;
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esac
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fi
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numcolors=$default_numcolors
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# Optionally detect and set the number of palette colors
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if [[ "$xflag" || -z "$Xflag" && -z "$nflag" && "$TERM" =~ ^xterm ]]; then
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# Since the VT340 only had a palette of 16 colors, we can vastly
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# improve the image if we tell xterm to increase it to 1024.
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# This would fail on a real VT340.
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palettechanged=yup
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oldnumcolors=$(getnumcolors)
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if [[ $oldnumcolors -lt 1024 ]]; then
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numcolors=$(setnumcolors 1024)
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if [[ $numcolors -le 0 ]]; then
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echo -e "\rTerminal did not accept escape sequence to increase color palette. Are you really an xterm?" >&2
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numcolors=$default_numcolors
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fi
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else
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# At least 1024 colors, so do not change anything
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numcolors=$oldnumcolors
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palettechanged=
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fi
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fi
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# Small optimization (saves half a second)
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if [[ $numcolors == 1024 ]]; then
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# Imagemagick already defaults to 1024 colors for sixel
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colors=""
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else
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colors="-colors $numcolors"
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fi
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# Print image filename after showing it? Yes, if multiple files.
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if [[ $# -gt 1 ]]; then
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showname=yup
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else
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showname=""
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fi
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# PAST IS PROLOGUE... NOW TO THE MEAT.
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for f; do
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x=$(convert "$f" $geometry $colors sixel:- 2>/dev/null)
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[[ ${#x} != 0 ]] || continue # The sixel command length better be >0
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: debugeta ${#x}
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case $0 in
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*sixgif)
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# If this program is named "sixgif" play files as animations,
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# instead of displaying each frame and scrolling down.
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echo -n $'\e[?80l' # Disable sixel scrolling
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for t in {1..3}; do
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echo -n "$x" # sixgif plays repeatedly
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done
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echo -n $'\e[?80h' # Reenable sixel scrolling
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;;
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*)
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echo -n "$x" # sixcat just shows once
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[[ "$showname" ]] && echo "$f"
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;;
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esac
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done
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# TIDY UP
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waitforterminal
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if [[ "$palettechanged" ]]; then
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# Reset color palette
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numcolors=$(resetnumcolors)
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: echo Number of colors reset to $numcolors >&2
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fi
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