"David A. Jones" <
[email protected]> writes:
> Ted,
>
> It was really early in the morning when I sent you my reply. I didn't intend
> to keep it
> off the fogo list so I'll put it on now. I hope that's ok with you?
Absolutely.
> Ok, here's my lame idea about capturing movement.
Not lame at all, similar to one or more approaches I noticed. Another
is where you overlay an image of nulled out space, eg where the trees
are so that you only care about movement in the rest of a certain
restricted area. With your grid approach you could simply ignore
certain grids, say 1, 5 and 4.
> 640x480 bitmap picture can be cut up into n squared pieces and to keep it
> simple let's cut the picture into 4 X 4 = 16 smaller squares thus 1/16 would
> represent
> a 40x30 bitmap.
> 640
> +--------+--------+--------+--------+
> | | | | |
> | | | | |
> | 1 | 2 | 3 | 4 |
> | | | | |
> +--------+--------+--------+--------+
> | | | | |
> | | | | |
> | 5 | 6 | 7 | 8 |
> | | | | |
> +--------+--------+--------+--------+ 480
> | | | | |
> | | | | |
> | 9 | 10 | 11 | 12 |
> | | | | |
> +--------+--------+--------+--------+
> | | | | |
> | | | | |
> | 13 | 14 | 15 | 16 |
> | | | | |
> +--------+--------+--------+--------+
>
>
> Now instead of diff'ing only one image of 640x480
> you would diff 16 images of 40x30.
>
> you'll have to tweak the diff percentage a bit say 10%
> for leaf wind rustling and just image noise which is acceptable changes.
>
> [let's leave time of day for later. (a) historical samples
> can smooth this out better so we need to keep some time of day
> samples around. (b) or we sample often that the differences in light
> will be negligible. (c) we can create a light table where we predict
> colour changes based on lighting dimming or brightening. ]
To handle time of day darkening you could compare the diffs of all the
grids simultaneously and see if they are universally changing as that
would mean:
a. it's getting dark out
b. some really large like an intergalactic spaceship is covering the
whole field of vision - in other words they're landing right on top of
us and your webcam, computer and everything else in the area will be
squashed anyway.
Clouds casting moving shadows will be tough.
> If there is significant changes(more than 10%) in section 13, 9, 5
> to 14, 10, 6 we can say the object is moving from
> left to right and someone should be alerted about this movement.
>
> same for top to bottom 1, 2, 3, 4 changed to 9, 10, 11, 12
>
> Maybe it's too simple but that's the principal I always use KISS, and it
> works great with the wife too.! :-)
Sometimes the most elegant software is the most simple.
--
Ted Guild <
[email protected]>
http://www.guilds.net