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#!/bin/bash
# Convert a huge .png file into smaller chunks for LeafletJS.
#
# Copyright (C) 2020 Markus Koch <markus@notsyncing.net>
#
# This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
# You can obtain a copy of the license at https://mozilla.org/MPL/2.0/.
# TODO: The width of the input png has to be a multiple of TILESIZE, otherwise bad things will happen.
# Workaround for now is to add white borders on the bottom and right:
# `convert $MAPFILE -extent ${crop}x${crop} -gravity NorthWest $MAPFILE.scaled.png`
TILESIZE=256
MAPNAME="world-2020-04-09"
MAPFILE="../$MAPNAME.png"
width=`file "$MAPFILE" | sed -n "s/.* \([0-9]\+\) x \([0-9]\+\).*/\1/p"`
crop=$TILESIZE
zoom=0
while true; do
out="$MAPNAME/$zoom"
tempfile=$out/temp.png
echo ""
echo "Generating maps for zoomlevel $zoom to $out..."
mkdir -p $out;
if [ ! -f "$tempfile" ]; then
if [ $crop -ge $width ]; then
echo " Reached max zoom at zoomlevel $zoom [using original zoom]"
cp $MAPFILE $tempfile
#convert $MAPFILE -extent ${crop}x${crop} -gravity NorthWest $tempfile
else
echo " Scaling map for zoomlevel $zoom"
convert $MAPFILE -resize ${crop}x${crop} $tempfile
fi
else
echo " Reusing existing scaled image"
fi
echo " Generating tiles..."
convert $tempfile -crop ${TILESIZE}x${TILESIZE} +adjoin $out/%05d.png
rm $tempfile
if [ $crop -ge $width ]; then
break;
fi
crop=$(($crop * 2))
zoom=$(($zoom + 1))
done;
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