#!/bin/bash

if [ -z "$1" ]; then

echo

echo "Clip videos into animated webp format."

echo

echo "Usage: $(basename "$0") <input_file> [start_time] [end_time] [output_name]"

echo

echo "Parameters:"

echo " input_file - Source video file"

echo " start_time - Start time (optional, format: HH:MM:SS)"

echo " end_time - End time (optional, format: HH:MM:SS)"

echo " output_name - Output filename without extension (optional)"

echo

echo "Output will be saved as <input_file>{-1,-2,etc}.webp in the same directory."

echo

echo "Environment variables:"

echo " SAMPLE - Sample time for crop detection (default: start_time or 1 second mark)"

echo " FRAMES - Number of frames to analyze for crop detection (default: 10)"

echo " SCALE - Output scale factor (default: 1) applied to cropped area"

echo " FPS - Output framerate (default: 20)"

echo

echo "Examples:"

echo " $(basename "$0") video.mp4 05 10"

echo " $(basename "$0") video.mp4 \"00:00:55\" \"00:01:12\""

echo " SCALE=0.25 $(basename "$0") video.mp4 05 10 video-thumbnail"

echo

echo "Which Produces:"

echo " video.webp"

echo " video-1.webp"

echo " video-thumbnail.webp"

echo

echo "ENV vars persist between runs, use unset to return to default."

echo " SCALE=0.8 $(basename "$0") video.mp4 0 10"

echo " $(basename "$0") video.mp4 10 20"

echo " SCALE=0.5 $(basename "$0") video.mp4 0 10"

echo " $(basename "$0") video.mp4 10 20"

echo " unset SCALE # resets to SCALE=1"

echo " $(basename "$0") video.mp4"

echo

echo "If cropdetect fails, try overriding SAMPLE position or increasing FRAMES"

echo " $ SAMPLE=5 FRAMES=20 $(basename "$0") video.mp4"

echo

exit 1

fi

if [ ! -f "$1" ]; then

echo "$1 not found"

exit 1

fi

function get_next_filename() {

local base="${1%.*}"

local ext="${1##*.}"

local newname="$1"

local counter=1

while [[ -f "$newname" ]]; do

newname="${base}-${counter}.${ext}"

((counter++))

done

echo "$newname"

}

if [ ! -z "$4" ]; then

out="${4%.webp}.webp"

else

dir=$(dirname "$1")

out=$(basename "$1")

out="$dir/${out%.*}.webp"

out=$(get_next_filename "$out")

fi

start=""

end=""

if [ ! -z "$2" ]; then

start="-ss $2 "

fi

if [ ! -z "$3" ]; then

end="-to $3 "

fi

if [ -z "$SAMPLE" ]; then

sample="$start"

else

sample="-ss ${SAMPLE:-1}"

fi

scale=${SCALE:-1}

fps=${FPS:-20}

frames=${FRAMES:-10}

crop=$(ffmpeg $sample -i "$1" -vframes $frames -vf cropdetect -f null - 2>&1 | grep -m 1 -oP 'crop=\K[0-9:]+')

if [ -z "$crop" ]; then

echo "cropdetect failed"

exit 1

fi

width=$(echo "$crop" | cut -d':' -f1)

width=$(echo "$width * $scale" | bc)

height=$(echo "$crop" | cut -d':' -f2)

height=$(echo "$height * $scale" | bc)

if [ -z "$width" ] || [ -z "$height" ]; then

echo "scaling failed"

exit 1

fi

if [ "$height" -gt "$width" ]; then

scale="-2:$height"

else

scale="$width:-2"

fi

# NOTE: fps=fps= is not a typo

ffmpeg -i "$1" $start $end -loop 1 -an -vf crop="$crop",scale="$scale",fps=fps="$fps" "$out"