lookup-image-map

lookup-image-map is a built-in function in `C source code'.

(lookup-image-map MAP X Y)

Lookup in image map MAP coordinates X and Y.
An image map is an alist where each element has the format (AREA ID PLIST).
An AREA is specified as either a rectangle, a circle, or a polygon:
A rectangle is a cons (rect . ((x0 . y0) . (x1 . y1))) specifying the
pixel coordinates of the upper left and bottom right corners.
A circle is a cons (circle . ((x0 . y0) . r)) specifying the center
and the radius of the circle; r may be a float or integer.
A polygon is a cons (poly . [x0 y0 x1 y1 ...]) where each pair in the
vector describes one corner in the polygon.
Returns the alist element for the first matching AREA in MAP.