111 lines
2.4 KiB
Bash
111 lines
2.4 KiB
Bash
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#!/bin/bash
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#
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# ---------------------------------------------------------
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#
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# script for Conway's Game of Life using ffmpeg filters
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#
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# usage: life.sh <input_image> <num_frames> <fps> <scale>
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#
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# example: life.sh gosper.png 200 12 10
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# would produce a 200 frame video of life from gosper.png
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# at 12 fps and 10x resolution of the original image.
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#
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# ---------------------------------------------------------
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#
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# nullprop - 2022
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set -e
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if [ "$#" -ne 4 ]; then
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echo "invalid number of parameters"
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echo "usage: life.sh <input_image> <num_frames> <fps> <scale>"
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exit
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fi
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INPUT=$1
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FRAMES=$2
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FPS=$3
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SCALE=$4
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rm -rf ./out
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mkdir out
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cp $INPUT out/frame-00000.png
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# check if pixel (X, Y) is alive
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is_alive () {
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echo "\
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eq( r(X,Y), 0)*\
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eq( g(X,Y), 0)*\
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eq( b(X,Y), 0)\
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"
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}
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# check if pixel (X, Y) with offset ($1, $2) is alive.
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# if position is outside image bounds, it is considered dead.
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is_alive_off () {
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echo "\
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eq( r(X$1,Y$2), 0)*\
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eq( g(X$1,Y$2), 0)*\
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eq( b(X$1,Y$2), 0)*\
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lt(X$1, W)*\
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gte(X$1, 0)*\
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lt(Y$2, H)*\
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gte(Y$2, 0)\
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"
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}
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# check if pixel (X, Y) has $1 neighbours
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has_neighbours () {
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echo "\
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eq(\
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$1,\
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$(is_alive_off -1 -1) +\
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$(is_alive_off -1 +0) +\
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$(is_alive_off -1 +1) +\
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$(is_alive_off +0 -1) +\
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$(is_alive_off +0 +1) +\
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$(is_alive_off +1 -1) +\
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$(is_alive_off +1 +0) +\
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$(is_alive_off +1 +1)\
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)\
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"
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}
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# should the pixel (X, Y) be alive?
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should_live () {
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echo "\
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$(is_alive)*$(has_neighbours 2) +\
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$(is_alive)*$(has_neighbours 3) +\
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ifnot($(is_alive), $(has_neighbours 3))
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"
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}
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# load image from $1,
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# step the game forward,
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# and save image to $2
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step () {
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ffmpeg \
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-i $1 \
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-vf \
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geq="\
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r='if( $(should_live), 0, 255 )':\
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b='if( $(should_live), 0, 255 )':\
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g='if( $(should_live), 0, 255 )':\
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a=255:
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interpolation=nearest" \
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$2
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}
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# generate frames
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for ((i=0; i<FRAMES; i++))
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do
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j=$((i+1))
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printf -v i_str "%05d" $i
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printf -v j_str "%05d" $j
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step out/frame-$i_str.png out/frame-$j_str.png
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done
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# combine to video
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ffmpeg -framerate $FPS -pattern_type glob -i 'out/frame-*.png' -c:v libx264 -pix_fmt yuv420p -vf scale="'$SCALE*iw:$SCALE*ih:flags=neighbor'" out/life.mp4
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