<div dir="ltr">morphological filters affect the shape <div style>they mostly work on binary images</div><div style>the most common are erode, dilate, close and open algorithm</div><div style>with which you can make a "pepper or salt removing filter" to remove black or white isolated pixels</div>
<div style><br></div><div style>concerning background subtraction, if you use a fixed background (you make a snapshot at startup and subtract it to the video stream) you will have defects due to light change, </div><div style>
some background part could be interpreted as a foreground feature</div><div style>adaptive background technique use a dynamic image reference, which could be made with a low-pass filter, this image is then subtracted to the video stream</div>
<div style>this makes a high-pass filter</div><div style><br></div><div style><br></div><div style><br></div></div><div class="gmail_extra"><br clear="all"><div>--<br>do it yourself <br><a href="http://antoine.villeret.free.fr" target="_blank">http://antoine.villeret.free.fr</a><br>
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<br><br><div class="gmail_quote">2013/4/18 Ska Frenz <span dir="ltr"><<a href="mailto:skafrenz@gmail.com" target="_blank">skafrenz@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div><div>Hi, thank you for the suggestions, I'll check openCv. Can you explain how to use "morphological filters" to clear up the noise in the image? Are there examples around? Also, could you please explain me better what do you mean with "adaptive background subtraction method"?<br>
<br></div>Thank you for your time :)<br><br></div>francesco<br></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">2013/4/17 Antoine Villeret <span dir="ltr"><<a href="mailto:antoine.villeret@gmail.com" target="_blank">antoine.villeret@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">hi, <div><br></div><div>the segmentation method (how you extract what is your interest from the rest of the image) is very critical in video tracking</div>
<div>background subtraction is a basic way to extract blob and it works only in certain conditions of light (if you want to track something outdoor, you should use an adaptive background subtraction method)</div>
<div>moreover, there is no general method to do video tracking, it depends on what you want to track and how it is filmed</div><div><br></div><div>so, the first thing is to have a good image, with not too much lighting changes, good contrast between background and features to track</div>
<div>then you can start thinking about segmentation, and the segmentation accuracy depends on the quality of the video</div><div>you may need to do something more than just background subtraction, for example, you could apply some morphological filter to remove noise</div>
<div>after that, you can start tracking<br></div><div>you could also apply a threshold on the blob size to not track very small blob</div><div>blob of interest are often surrounded by very small blobs due to segmentation noise</div>
<div><br></div><div>but you can have a look at pix_opencv objects,</div><div>there is [pix_opencv_blobtrack] which implements a whole processing chain, including foreground extractor, blob detector, blob tracker and follower</div>
<div>I'm not sure it's included in pd-extended, but you can find some binaries on build server</div><div><br></div><div>hope this help</div><div><br></div><div>antoine</div><div>
<br></div></div><div class="gmail_extra"><br clear="all"><div>--<br>do it yourself <br><a href="http://antoine.villeret.free.fr" target="_blank">http://antoine.villeret.free.fr</a><br></div>
<br><br><div class="gmail_quote">2013/4/17 Ska Frenz <span dir="ltr"><<a href="mailto:skafrenz@gmail.com" target="_blank">skafrenz@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div>
<div dir="ltr"><div><div><div>Hi everyone, this is my first time on the pd-list so I hope I won't do anything wrong. <br></div>I'm
writing here to get some help about pd tracking objects (pix_blob..).
I'm using the background subtraction method, to track objects and I need
help to understand how I can track multiple objects with multiples
different blobs. I'm trying the pix_multiblob and yes, it show 2
blobs..but they track the same object. Then basically I do not
understand how can I make the first blob to follow just one object for
all the time that specific object is inside the webcam rectangle, and
the second blob to track another separate object. I cannot find any
material that clearly talks about this.I attached the patch I'm working on. I'd love to see some well-explained examples if you know where to
get them.<br>
</div>Thank you very much for your help :)<br><br></div>Francesco</div>
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