🚀 go-pugleaf

In article <1j781hINNih7@shelley.u.washington.edu> dean2@tbone.biol.scarolina.edu (Dean Pentcheff) writes:
>Image analysis people:  I've got a puzzling problem.
>
>Here's the setup:  For various obscure reasons, I'm doing some analysis
>on some videotapes.  Using a realtime video analysis system (Datacube),
>I'm trying to get average pixel intensities in a set of nested areas.
>The areas are 1x1 pixel, 2x2, 4x4, 8x8, and 16x16 pixels.  The 1x1 area
>is in the center, the 2x2 framed around it, the 4x4 framed around that,
>etc.
>
>On each video frame I'm reading the (B&W) pixel intensities from all
>the pixels in each of the boxes.  For each box, the pixel intensities
>are summed and divided (all floating point - not integer) by the number
>of pixels in the box.
>
>Here's the puzzling problem.  During "boring" times (when there's
>little action in the video image) the average intensities are:  2x2 >
>4x4 > 1x1 > 8x8 > 16x16.  Huh?  Why should this be?  Based on several
>tries on various images, this is consistent.  The same pattern is
>somewhat evident when images are moving around, but of course there are
>confusing effects due to bright patches hitting parts of the outer
>boxes, but not some of smaller, inner boxes, etc.

How about calculating standard deviations along with your means.  You will
probably find that there is no statistically signficant difference between
the measurements.

Just a guess, but you may be seeing a noise difference between video
fields.

>-Dean 
Greg