[PD] Gem image analysis

[IOhannes m zmoelnig]

chris clepper wrote:
> 
> On May 30, 2005, at 9:34 PM, Thomas Ouellet Fredericks wrote:
> 
>> Again:
>>
>> Use pix_movement.
>> Analyse with [pix_blob 4] (alpha channel)
>> The last outlet of pix_blob gives you the amount of movement in the
>> image.
> 
> 
> The last outlet is for the Z axis and, as near as I can tell, the code
whatever "Z" means.
it definitely knows nothing about the z-axis in a 3dimensional space.

> measures how bright the image is by dividing the sum of all of the
> selected channels by the maximum possible sum for the image.  So if the
> image was entirely white (R,G,B all = 255) it would give a 1.0 and a
> black image would be 0.0.


so the last outlet is a measure of the size of the blob.
if you use [pix_movement] to convert motion (== change of data in a
series of images) into an image (the difference between the sequence of
images), then the blob-size is a measure of the amount of movement
(between to subsequent images).

so the blobsize is somewhat like the overall "brightness" of the blob.

using [pix_background] instead of [pix_movement] _could_ produce better
results, but i think this really depends on your set up.
if you are not  sure, experiment with both and see what gives better
results.

> 
> My method to measure change over time or from a reference image would
> act as a trigger, which is I believe what Max wants to do.

well, if he does "NOT want to TRACK anything" but just detect if there
is any movement in the image, your suggestion seems to be a bit
overpowered (nonetheless it should work fine)

mfg.cas.dr
IOhannes

> 
> cgc
> 
> 
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