WebComics/XkcdClickAndDrag

Big.

No, literally it contains 81 by 32 tiles each being 2048 by 2048 (some sparse). So that's nearly an 11 gigapixel image, stored in 6MB of 225 PNG tiles, for a full resolution of 165888 by 65536. I have it compressed into a 15MB PNG file, but good luck finding a viewer that will cope.

Code to build full image:

 #!/bin/bash

 LOWX=33
 HIGHX=48
 LOWY=13
 HIGHY=19

 echo "P1 1 1 0" | pnmscale 2048 >nblank.pnm
 echo "P1 1 1 1" | pnmscale 2048 >sblank.pnm

 for y in `seq -f "%gn" $LOWY -1 1` `seq -f "%gs" $HIGHY` ; do
 	for x in `seq -f "%gw" $LOWX  -1 1` `seq -f "%ge" $HIGHX` ; do
 		if ! test -e "$y$x.pnm" ; then
 			if ! test -e "$y$x.png" ; then
 				wget http://imgs.xkcd.com/clickdrag/$y$x.png
 			fi
 			if test -e "$y$x.png" ; then
 				pngtopnm <$y$x.png | ppmtopgm >$y$x.pnm
 			else
 				if test "n" = "`echo $y | sed -e "s/^.*\(.\)$/\1/"`" ; then
 					ln -s nblank.pnm $y$x.pnm
 				else
 					ln -s sblank.pnm $y$x.pnm
 				fi
 			fi
 		fi
 	done
 done

 for y in `seq -f "%gn" $LOWY -1 1` `seq -f "%gs" $HIGHY` ; do
 	echo pnmcat -leftright `seq -f "$y%gw.pnm" $LOWX  -1 1` `seq -f "$y%ge.pnm" $HIGHX`
 	pnmcat -leftright `seq -f "$y%gw.pnm" $LOWX  -1 1` `seq -f "$y%ge.pnm" $HIGHX` >$y.pnm
 done
 echo pnmcat -topbottom `seq -f "%gn.pnm" $LOWY -1 1` `seq -f "%gs.pnm" $HIGHY`
 pnmcat -topbottom `seq -f "%gn.pnm" $LOWY -1 1` `seq -f "%gs.pnm" $HIGHY` >all.pnm
 pnmscale -reduce 8 all.pnm | pnmtopng >all_reduced.png
 pnmtopng all.pnm >all.png

Note the ppmtopgm stage - this is because one of the tiles appears to be saved as a colour PNG rather than a greyscale PNG, even though it contains a greyscale image. This stage prevents the output file (all.pnm which is 9.5GB in size) from being three times the size.

http://blackhole12.blogspot.com/2012/09/analyzing-xkcd-click-and-drag.html