This program had a couple of those forehead-slapping moments.
In early November, I'd moved my web pages from www.dnaco.net to
www.canonical.org, but www.dnaco.net was still getting hits --- one of
my pages referred explicitly to its imagemap.cgi program, because it
had a server-side imagemap in it. Forehead slap number one.
Well, I figured maybe I should install imagemap.cgi on
www.canonical.org. But after searching for a while, I found a lot
more about security holes in imagemap.cgi (Rob McCool wrote it, so it
was full of buffer overflows) than about where to download it. So I
figured I'd write my own, in Python.
So I took an afternoon and wrote it and got it working and installed
it. Then I thought I'd see if I could find documentation on the file
format. And I discovered that Apache, which is what we use on
www.canonical.org, ships with a module that has the functionality of
imagemap.cgi.
Forehead slap number two. I was insufficiently lazy and did hours of
work for no good reason --- someone else had already done them!
(For people who are mystified by the references to forehead slapping:
people from the US sometimes slap their foreheads when they learn
something that surprises them, especially when it demonstrates how
stupid they have been before.)
So I added another interface to this program, one to convert
server-side imagemaps to client-side HTML imagemaps. (Someone probably
already did that, too; I didn't look) I used this to improve the web
page.
So here's pymagemap.py, which works as a CGI script if you run it from
the command line:
#!/usr/bin/env python
# CGI script for imagemaps, to replace the old C imagemap program from NCSA.
# Uses PATH_TRANSLATED to get the map file. Parses '#' comment lines,
# 'default url' lines, and 'rect url x,y x2,y2' lines to come up with
# an image map; then it fetches the x,y QUERY_STRING and generates a redirect.
import os, sys, string, re, string
def startswith(haystack, prefix):
length = len(prefix)
return haystack[:length] == prefix
def complain(str):
print "Content-type: text/plain\n\n" + str + "\n"
sys.exit(-1)
def getcoords(source, str):
coords = string.split(str, ',')
if len(coords) != 2:
complain("%s: weird coords %s in %s" %
(sys.argv[0], str, source))
return map(int, coords)
def distsq(x1, y1, x2, y2):
dx = x1 - x2
dy = y1 - y2
return dx*dx + dy*dy
blanklinere = re.compile('\s*$')
class Map:
def __init__(self, filename):
f = open(filename)
self.rects = []
for line in f.readlines():
if startswith(line, '#') or blanklinere.match(line):
continue
fields = string.split(line)
if fields[0] == 'default':
self.default = fields[1]
elif fields[0] == 'rect':
url, corner1, corner2 = fields[1:]
x1, y1 = getcoords("%s line %s" % (filename, line), corner1)
x2, y2 = getcoords("%s line %s" % (filename, line), corner2)
# let them be any two corners, not just upper left and lower
# right, in that order
if x1 > x2: x1, x2 = x2, x1
if y1 > y2: y1, y2 = y2, y1
self.rects.append((url, x1, y1, x2, y2))
else:
# don't want to send this to the web browser
# it might reveal secret file contents
sys.stderr.write("%s: Can't understand line %s in mapfile %s" %
(sys.argv[0], line, filename))
complain("Bad mapfile --- see server error log for details\n")
def geturl(self, x, y):
# possible shapes
possibles = []
# find the rectangles the coords are in
for rect in self.rects:
url, x1, y1, x2, y2 = rect
if x1 < x and x < x2 and y1 < y and y < y2:
possibles.append((url, (x1 + x2)/2, (y1 + y2)/2))
# of all the shapes the coords are in, return the one whose center
# is closest
mindist = None
besturl = self.default
for shape in possibles:
url, centerx, centery = shape
dist = distsq(x, y, centerx, centery)
if mindist is None or mindist > dist:
mindist = dist
besturl = url
return besturl
def html(self, name):
def htmlrect(rect):
url, x1, y1, x2, y2 = rect
return (' <area shape="rect" coords="%d,%d,%d,%d" href="%s" />\n' %
(x1, y1, x2, y2, url))
return ('<map name="%s">\n' % name +
string.join(map(htmlrect, self.rects), '') +
"</map>\n")
def main():
# default to no query string
qs = os.environ.get('QUERY_STRING', '')
# can't do that with PATH_TRANSLATED
if os.environ.has_key('PATH_TRANSLATED'):
mapfile = os.environ['PATH_TRANSLATED']
else:
complain("No PATH_TRANSLATED provided.\n" +
"You need to put something after %s in the URL.\n"
% sys.argv[0])
map = Map(mapfile)
if qs == '':
url = map.default
else:
coords = getcoords("user input", qs)
url = map.geturl(coords[0], coords[1])
print "Location: %s\n\n" % url
if __name__ == '__main__': main()
Here's pymagemap.cgi, which is useful if your web server likes CGI
scripts to have filenames that end in .cgi:
#!/usr/bin/env python
import pymagemap
pymagemap.main()
And here's imagemap2html:
#!/usr/bin/env python
import sys, pymagemap
map = pymagemap.Map(sys.argv[1])
sys.stdout.write(map.html(sys.argv[2]))
