It finds the following lines in the file .../site.imap/htdocs /bench.map:
rect left.html 0,0 118,144 rect right.html 118,0 237,144 #point left.html 59,72 #point right.html 177,72 #poly left.html 0,0 118,0 118,144 0,144 #poly things 0,0 118,0 118,144 0,144 #poly right.html 118,0 237,0 237,144 118,114 #circle left.html 59,72 118,72 #circle things 59,72 118,72 #circle right.html 177,72 237,72 default default.html
The coordinates start from 0,0, the top-lefthand corner of the image.
rects are rectangles with the top-left and
bottom-right corners at the two x,y positions shown.
points are points at the x,y position.
polys are polygons with between 3 and 100 corners
at the x,ys shown. circles have their center at
the first x,y — the second is a point on the circle. The point
nearest to the cursor is returned; otherwise, the closed figure that
encloses the cursor is not returned. As it stands only the
rects are left uncommented. They set up two areas
in the left and right halves of the image and designate the files
left.html and right.html
to be returned if the mouse click occurs in the
corresponding rectangle. Notice that the points are expressed as
x,y <whitespace>. If you click in
the left rectangle, the URL
www.butterthlies.com/left.html is accessed, and
you see the message:
You like to sit on the left
and conversely for clicks on the right side. In a real application, these files would be menus leading in different directions; here they are simple text files:
You like to sit on the left You like to sit on the right
In a real system, you might now want to display the contents of
another directory, rather than the contents of a file (which might be
an HTML document that itself is a menu). To demonstrate this, we have
a directory, ... /htdocs/things, which contains
the rubbish files 1, 2,
3. If we replace left.html in
bench.map with things, as
follows:
rect things 0,0 118,144 rect right.html 118,0 237,144
we see:
Index of /things . Parent Directory . 1 . 2 . 3
You do not have to restart Apache when you change
bench.map, and the formatting of this menu is
not affected by the setting for IMapMenu.
How do we know what the coordinates of the rectangles are (for
instance, 0,0
118,144)? If we
access sides.html and put the cursor on the
picture of the bench, Netscape/MSIE helpfully prints its coordinates
on the screen — following the URL and displayed in a little
window at the bottom of the frame. For instance:
http://192.168.123.2/bench.map?98,125
It is quite easy to miss this if the Netscape window is too narrow or stretches off the bottom of the screen. We can then jot down on a bit of paper that the picture runs from 0,0 at the top-left corner to 237,144 at the bottom-right. Half of 237 is 118.5, so 118 will do as the dividing line.
We divided the image of the bench into two rectangles:
0,0 118,144 118,0 237,144
These are the center points of these two rectangles:
59,72 177,72
so we can rewrite bench.map as:
point left.html 59,72 point right.html 177,72
and get the same effect.
The version of bench.map for polygons looks like this:
poly left.html 0,0 118,0 118,144 0,144 poly right.html 118,0 237,0 237,144 118,114
For circles, we use these points as centers and add 118/2=59 to the x-coordinates for the radius. This should give us two circles in which the cursor is detected and the rest of the picture (right in the corners, for instance) in which it is not:
circle left.html 59,72 118,72 circle right.html 177,72 237,72
When things go
wrong with ImageMaps — which we can engineer
by setting circlesin bench.map
and clicking on the corners of the picture — the
action to take is set first by a line in the file bench.map
:
default [error|nocontent|map|referer|URL]
The meanings of the arguments are given under the
ImapDefaultabove. If this
line is not present, then the directive
ImapDefault takes over. In this case we set:
default default.html
and the file default.html is displayed, which says:
You are clicking in the wrong place.