[PD] Gem image analysis

[Max Neupert]

thanks IOhannes, now i've got it.


Am 31.05.2005 um 09:07 schrieb 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)