Dear Joelle, Curious by your question, I tried it immediately on a simple 3 by 3 pixel raster map with your pixelvalues in it. I have the most recent ILWIS 3.12 in use. I applied the avg3x3 filter and I obtained the expected 1765.667 for the central pixel (in case of course, I put the decimal output precision on 0.001) Hence I cannot yet explain your outcome.
On the other hand, if I put the precision on 100 (so the outcome will be rounded to the nearest multiple of 100), I get indeed the central average equal to 1800. Could this explain your results? Succes Jan Hendrikse ITC / ILWIS team -----Original Message----- From: Joelle Dagnelies [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 23, 2003 09:56 To: Ilwis list Subject: (ilwis-list) filter avg 3x3 Dear list members, I have a question concerning the avg3x3 filter : I used this filter on an image, and wanted to verify the result. For this, I choosed a pixel in the original image (in the central part of the image) (with DN = 2507, see below), made the mean with it and its 8 surrounding pixels (result : 1765.667) and compared the result with the same pixel in the filtered image (result : 1800 !?). Can somebody explain me where this value is coming from ? maybe I didn't understand the filter avg3x3 principle ?!... pixel and its surroundings : 1050 1948 1771 1204 2507 2641 827 1782 2161 Thank you, Joelle _________________________________________________________________ ________________________________________________________ To leave the ILWIS-LIST discussion list, send a email with 'unsubscribe ilwis-list' in the body to '[EMAIL PROTECTED]'
