Convert raster images of Slazav's map series (https://slazav.xyz/maps/podm.htm) to Garmin JNX format files

Makefile

.SUFFIXES:

map_files := $(wildcard *.map)
jnx_files := $(map_files:%.map=%.jnx)

.PHONY: all
all: $(jnx_files)

%.jnx: %.png %.map
	bash slazav2jnx.sh $^ $@

clean:
	rm -f $(jnx_files)

slazav-map.awk

#! /usr/bin/env awk -f

# Copyright (C) 2020 Dmitry Efremov <defremov аt aha dоt ru>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

function mins_to_dec_degs(degs, mins, hemi) {
	sign = (hemi == "S" || hemi == "W") ? -1 : 1
	return sign * (degs + mins / 60.)
}

function expand_bounds(lat, lon) {
	if (lat < minlat) minlat = lat
	if (lon < minlon) minlon = lon
	if (lat > maxlat) maxlat = lat
	if (lon > maxlon) maxlon = lon
}

BEGIN {
	_abort = 0

	FS = "\\s*,\\s*"
	CONVFMT = "%.8f"

	minlat = 90.
	maxlat = -90.
	minlon = 180.
	maxlon = -180.

	if (!gcp_cmd) {
		gcp_cmd = "cat"
	}

	i = 0
}

/^Point[0-9]{2},xy,\s*[0-9]+,/ {
	xy[i++]= $3 " " $4
	lat = mins_to_dec_degs($7, $8, $9)
	lon = mins_to_dec_degs($10, $11, $12)
	print lon " " lat |& gcp_cmd

	expand_bounds(lat, lon)
}

END {
	if (_abort) {
		exit _abort
	}

	if (!extents_file) {
		extents_file = "/dev/stdout"
	}

	print minlon, minlat >extents_file
	print maxlon, maxlat >extents_file

	if (!gcp_file) {
		gcp_file = "/dev/stdout"
	}

	close(gcp_cmd, "to")
	i = 0
	while ((gcp_cmd |& getline lonlat) > 0) {
		sub(/\s+0$/, "", lonlat)
		print xy[i++] " " lonlat >gcp_file
	}
	close(gcp_cmd)
}

slazav2jnx.sh

#! /usr/bin/env bash

# This script converts raster images of Slazav's map series
# (https://slazav.xyz/maps/podm.htm) to Garmin JNX format
# files.
#
# Depends on: gawk, map2jnx tool and GDAL utilities.
#
# Example: to convert N55aE037 sheet to JNX format download
# N55aE037.png and N55aE037.map files then run:
# slazav2jnx.sh N55aE037.{png,map} N55aE037.jnx
#
# Copyright (C) 2020 Dmitry Efremov <defremov аt aha dоt ru>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

set -Eeuo pipefail

PATH=/sbin:/usr/sbin:/bin:/usr/bin
export PATH

progname="${0##*/}"
slazav_map="$(dirname "$0")/slazav-map.awk"

declare -a tmpfiles

map2jnx=qmt_map2jnx

# Suitable for a 160×240 display
declare -a jnx_scale_values=(31250 7813 5209 2084 1303)

slazav_map_image=''
slazav_map_data_file=''
jnx_file=''
jnx_title=''

newtmp() {
	while (( $# )) ; do
		tmpfiles=($(mktemp) ${tmpfiles[@]})
		eval "${1}=${tmpfiles}"
		shift
	done
}

term_handler() {
	local signal="${1}"
	>&2 printf "\n%s: caught %s signal, exiting.\n" \
		"${progname}" "${signal}"
	exit 1
}

set_signal_handlers() {
	trap 'set +e ; kill $(jobs -p) 2>/dev/null ; \
		rm -f ${tmpfiles[@]}' EXIT
	for signal in INT QUIT TERM ; do
		trap 'term_handler "${signal}"' ${signal}
	done
}

usage() {
	cat <<EOF
${progname} script converts raster images of Slazav's map series
(http://slazav.mccme.ru/maps/podm/index.htm) to Garmin JNX format
files.

Usage: ${progname} [options] map_image map_data_file jnx_file [jnx_title]
Options:
	-h	show this help message and exit

Depends on: gawk, map2jnx tool and GDAL utilities.

Example: to convert N55aE037 sheet to JNX format download N55aE037.png
and N55aE037.map files then run:
${progname} N55aE037.{png,map} N55aE037.jnx 'Slazav N55aE037'
EOF
}

parse_parameters() {
	while getopts "hn" OPT; do
		case "${OPT}" in
		h)
			usage
			exit 0
			;;
		\?)
			echo
			>&2 usage
			exit 1
			;;
		esac
	done
	shift $((${OPTIND} - 1))

	if [[ $# -lt 3 ]] ; then
		>&2 printf \
			"${progname}: script requires 3 arguments.\n\n"
		>&2 usage
		exit 1
	fi

	slazav_map_image="${1}"
	slazav_map_data_file="${2}"
	jnx_file="${3}"
	jnx_title="${4:-${jnx_file%.*}}"
}

slazav2jnx() {
	# Extract ground control points data and the map extents from
	# the supplied map data file (.map).
	# The GCPs are reprojected from WGS 84 to Pulkovo 1942 /
	# Gauss-Kruger zone 7 coordinate system
	local pulkovo_42_gcps
	local cmd='gdaltransform -s_srs EPSG:4326 -t_srs EPSG:28407'
	newtmp pulkovo_42_gcps
	local wgs_84_extents=$(awk -f "${slazav_map}" \
		-v gcp_cmd="${cmd}" -v gcp_file="${pulkovo_42_gcps}" \
		"${slazav_map_data_file}")

	# Convert the supplied source map image to 24-bit RGB GeoTIFF
	# format and make it georeferenced by adding the GCPs from the
	# previous step
	local pulkovo_42_gcp_image
	newtmp pulkovo_42_gcp_image
	gdal_translate -of GTiff -expand rgb\
		$(awk '{print " -gcp", $0}' "${pulkovo_42_gcps}") \
		-a_srs EPSG:28407 \
		"${slazav_map_image}" "${pulkovo_42_gcp_image}"

	# Reproject the extents of the source map from WGS 84 to the
	# World Mercator coordinate system
	local world_mercator_extents=$(gdaltransform -s_srs EPSG:4326 \
		-t_srs EPSG:3395 <<<"${wgs_84_extents}" | \
		awk '{print $1, $2}')

	# Reproject the georeferenced image to the World Mercator CS
	local world_mercator_prj_image
	newtmp world_mercator_prj_image
	gdalwarp -t_srs EPSG:3395 \
		-te ${world_mercator_extents} -of GTiff -overwrite \
		"${pulkovo_42_gcp_image}" "${world_mercator_prj_image}"

	# Get the width and height in pixels of the World Mercator
	# image
	declare -a pixel_size=($(gdalinfo \
		"${world_mercator_prj_image}" | awk -F',\\s*' \
		'/^Size is / {sub(/^[^0-9]*/, ""); print $1, $2}'))

	# Reproject the georeferenced image from Pulkovo 42 to WGS 84
	# CS and downscale it to a set of level of detail images using
	# the width and height in pixels from the previous step
	local level_image
	declare -a level_images
	for n in "${!jnx_scale_values[@]}" ; do
		newtmp level_image
		level_images=(${level_image} ${level_images[@]})
		# Halve the resolution of each successive level
		gdalwarp -t_srs EPSG:4326 -r cubic \
			-te ${wgs_84_extents} \
			-ts $(( (${pixel_size[0]} + $n) >> $n )) \
			$(( (${pixel_size[1]} + $n) >> $n )) \
			-of GTiff -overwrite \
			"${pulkovo_42_gcp_image}" "${level_image}"
	done

	# Convert the set of level of detail images to a JNX file
	local x_param=${jnx_scale_values[@]}
	"${map2jnx}" -q 90 -s 444 -x ${x_param// /,} \
		-p 90 -m "${jnx_title}" "${level_images[@]}" \
		"${jnx_file}"
}

main() {
	set_signal_handlers
	parse_parameters "${@}"

	slazav2jnx

	exit 0
}

main "${@}"