Path: utzoo!utgpu!watmath!clyde!att!whuts!homxb!homxc!jackson
From: jackson@homxc.ATT.COM (B.JACKSON)
Newsgroups: comp.graphics
Subject: How do I find the area of a non-polygonal bounded region?
Keywords: area fill computer graphics
Message-ID: <5532@homxc.ATT.COM>
Date: 14 Feb 89 02:06:27 GMT
Distribution: na
Organization: AT&T BL Holmdel NJ USA
Lines: 33

Here's the problem:  I've got a bitmapped display 
that has an image of a ragged-edged closed perimeter surrounding an
open area.  I need to know the area of the opening.  The
boundry of the area looks like someone spray-painted a
circle of pixels on the screen -- I can guarentee a closed
boundry of connected pixels, but there are some individual
pixels (and groups of pixels) 'floating' around out in the
area I want to measure (I don't want to count the 'floaters'
in the area).  The perimeter has, as you might
guess, thousands of small inclusions.

My first guess at how to measure the area is to perform a
"fill" operation and count the number of pixels I generate
to do the fill -- but I'm open to suggestions. 
(I can guarentee I can plant a seed pixel in a clear
space within the circle if that helps.)

If anyone has a recommended algorithm for finding the
enclosed area (or for doing a fill on an arbitrarily-bounded
region) please let me know.  If you've got source code
for solving such a problem (or can point me to a
reference that does) I will be even more grateful!

Thanks in advance,

B. Scott Jackson
Room 3D-418
AT&T Bell Laboratories
Crawford's Corner Rd.
Holmdel, NJ  07733

(201) 949-6495
homxc!jackson