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Main
Date: 09 Dec 2006 18:05:58
From: W. Watson
Subject: Software for Making a Digital Sky Mask?
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I have an unusual application that can require a digital sky mask to
recognize areas of potential movement, and areas where there may be movement
but the device (a camera) should ignore movement there. The mask building
exercise is this.
Take an all-sky image of the entire sky that includes all nearby land
obstacles like trees, and homes. Now build digital mask with certain
properties. Mark all areas where there's complete visibility by assigning
each pixel in these areas a value of say 50. This indicates a pixel value
must be more than 50 to cause detection. Generally anything above tree level
qualifies for these areas. Next mark areas like a neighbor's light the value
255 to indicate any value detected should not trigger detection. The
resulting, tiff, file is a grey scale file with pixel values from 0 to 255.
So here's the question.
Is there any software out there that is specifically designed to handle
something like this easily. I've looked at programs like Corel's Paint Shop
Pro, Gimp (Linux), and Adobe Elements. One can do these things with them,
but the learning curve is steep. The idea is to lessen the steepness.
Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
--
"Suppose you were an idiot. And suppose you were a
member of Congress. But I repeat myself."
-- Mark Twain
Web Page: <home.earthlink.net/~mtnviews >
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Date: 09 Dec 2006 12:29:12
From: Chris L Peterson
Subject: Re: Software for Making a Digital Sky Mask?
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On Sat, 09 Dec 2006 18:05:58 GMT, "W. Watson" <wolf_tracks@invalid.com >
wrote:
>Take an all-sky image of the entire sky that includes all nearby land
>obstacles like trees, and homes. Now build digital mask with certain
>properties. Mark all areas where there's complete visibility by assigning
>each pixel in these areas a value of say 50. This indicates a pixel value
>must be more than 50 to cause detection. Generally anything above tree level
>qualifies for these areas. Next mark areas like a neighbor's light the value
>255 to indicate any value detected should not trigger detection. The
>resulting, tiff, file is a grey scale file with pixel values from 0 to 255.
I use a much simpler mask with my allsky camera. I start with a twilight
image, bring it in to Photoshop, and mask out all the areas I want to
ignore. Those I fill with black. Everything else is white. This is
converted to a 1-bit per pixel bitmap and saved. That image is simply
multiplied into the incoming frames before processing (Metrec does this,
but so will many applications). I'm not sure there would be any added
value to a mask with a variable threshold, and it might slow down
processing on a live video stream.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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