A program to wrap ffmpeg specifically for usage with gifs. Allows speed manipulation and time clipping.

giftool

#!/bin/bash

POSITIONAL=()
while [[ $# -gt 0 ]]
do
key="$1"

case $key in
    -b|--begin|-ss)
    START="$2"
    shift # past argument
    shift # past value
    ;;
    -l|--length)
    LENGTH="true"
    shift # past argument
    ;;
    -t|--time)
    TIME="$2"
    shift # past argument
    shift # past value
    ;;
    -s|--speed)
    SPEED="$2"
    shift # past argument
    shift # past value
    ;;
    -o|--outfile)
    OUTFILE="$2"
    shift # past argument
    shift # past value
    ;;
    -h|--help)
    echo "
Usage: giftool <OPTIONS> filename
    -b|--begin|-ss:  The starting point to use in the video in seconds
    -t|--time:       The length of the video in seconds after the start point
    -l|--length:     Print the length of the file in seconds and exit
    -s|--speed:      The factor by which to speed up or slow down the video
    -o|--outfile:    The file name to use for the resultant file
    -h|--help:       Show this message and exit
"
    exit 0
    ;;
    *)    # unknown option
    POSITIONAL+=("$1") # save it in an array for later
    shift # past argument
    ;;
esac
done
set -- "${POSITIONAL[@]}" # restore positional parameters

if [[ -n $1 ]]; then
    FILE="$1"
    if [ ! -f "$FILE" ]; then
        echo "File does not exist; exiting"
        exit -1
    fi
else
    echo "No filename provided; exiting"
    exit 0
fi

if [[ -n $LENGTH ]]; then
    if hash exiftool 2>/dev/null; then
        exiftool -Duration $FILE | grep -Eo '[0-9]+\.*[0-9]+'
    else
        echo "exiftool is required for this functionality"
    fi
    exit 0
fi

if ! hash ffmpeg 2>/dev/null; then
    echo "ffmpeg is required for this program to work properly"
    exit -1
fi

## Get random tmp file for palette
paletteFile=/tmp/$RANDOM-palette.png

## Trap exit to make sure we clean up our tmp file
function finish {
        rm "$paletteFile"
}
trap finish EXIT

filterCmd="-i '$1' -vf \ scale=iw:ih:flags=lanczos,palettegen $paletteFile &>/dev/null"
cmd="-i $1 -i '$paletteFile' -filter_complex 'scale=iw:ih:flags=lanczos[x];[x][1:v]paletteuse"
outfile="${1%%.*}"

if [[ -n $SPEED ]]; then
    cmd=$cmd',setpts='$(bc -l <<< "1/"$SPEED | sed -e 's/[0]*$//g')'*PTS'"'"
    outfile="$outfile-x$SPEED"
else
    cmd=$cmd"'"
fi

if [[ -n $TIME ]]; then
    filterCmd="-t $TIME $filterCmd"
    cmd="-t $TIME $cmd"
    if [[ -z ${START+x} ]]; then
        outfile="clipped-$outfile-0-$TIME"
    fi
fi

if [[ -n $START ]]; then
    filterCmd="-ss $START $filterCmd"
    cmd="-ss $START $cmd"
    if [[ -n $TIME ]]; then
        outfile="clipped-$outfile-$START-$(bc -l <<< "$START+$TIME")"
    else
        outfile="clipped-$outfile-$START-end"
    fi
fi

if [[ -n $OUTFILE ]]; then
    outfile=$OUTFILE
else
    outfile="$outfile.gif"
fi
cmd="$cmd $outfile -v quiet -progress /dev/stdout 2>&1 > /dev/null"

eval "ffmpeg $filterCmd"
eval "ffmpeg $cmd"
exit 0