User:Olpl/NationalGallery

A script to download high-resolution images of paintings in the National Gallery collection.

Prerequisites

• Bash
• ImageMagick (sudo apt-get install imagemagick)

Usage

zoom.sh <contentId>

E.g.

zoom.sh 6509

(Please don't upload this example image. It already exists at the Commons as Image:RokebyVenus.jpg.)

zoom.sh

#!/bin/bash
if [ -z "$1" ] ; then echo "Usage: $0 contentId" >&2 ; exit 1 ; fi

# maximum zoom level
ZOOM="07"

# strings they use to obfuscate
TRFROM=0123456789
TRTO=vRfOdXapKz

# estimated limits
COLS=40
ROWS=40

# directory to store downloaded fragments
CACHE=cache/$1
mkdir -pv $CACHE

CONTENTID=$(printf "%05d" $1)

WGET="wget -nv "

for col in `seq -w 00 $COLS`; do
	for row in `seq -w 00 $ROWS`; do
		DEST="$CACHE/r$row-c$col.jpg"
		
		if [ ! -f "$DEST" ]; then	
			#obfuscated tile ID
			TILE=$(echo "$row$CONTENTID$col$ZOOM" | tr $TRFROM $TRTO)
			$WGET -O $DEST "http://www.nationalgallery.org.uk/custom/ng/tile.php?id=$TILE"
		fi;
		
		if [ ! -s "$DEST" ]; then
			if [ "$col" -eq "00" ]; then
				ROWS=$(printf "%02d" $(( 10#$row - 1 )))
				echo "New max ROWS = $ROWS";
				break;
			else
				if [ "$row" -eq "00" ]; then
					echo "Final column is $col";
					break 2;
				fi
			fi;
		fi;
		
	done;
done;

montage `find $CACHE -type f ! -size 0 | sort` -tile ${col}x -geometry +0+0 ${CONTENTID}.jpg

ls -lh ${CONTENTID}.jpg

Alternatives

Alternatively, you can use Ruby-based natgal-dl from Paul Battley.