Spaces and tabs have no meaning whatsoever, and can be inserted at will. All lines starting with a '#' are to be taken as a comments.
(X1,Y1)-(X2,Y2) URL
Any point inside the box X1,Y1 to X2,Y2 will return the url URL

(X1,Y1),R URL
Any point inside the circle with the origo in X1,Y1 and the radius R will return the url URL.

(X,Y) URL
If more than one point is specified in the file, the one closest to the position the user pressed will be used.

ppm:PPM file
Use the PPM file refered to by the absolute filesystem path 'PPM file' as a map file. Each color in that file may point to a different document.

pgm:PGM file
As PPM, but the file is a greyscale file.

color:(r,g,b):URL
In all PPM: files referenced, this color will point to the document URL. r,g and b is decimal integers between 0 and 255. If the file searched is a PGM (greyscale) picture, the greyscale will be (r+g+b)/3.

color:(r,g,b)-(r,g,b):URL
All colors in the range will point to URL. If the file searched is a PGM (greyscale) picture, the greyscale will be (r+g+b)/3.

color:greyscale-greyscale:URL
All colors with an intensity falling within the range will point to URL.

color:greyscale:URL
All colors with the intensity greyscale will point to URL.

default:URL
The url URL will be returned if nothing else matched.