cathair28

You can use the edge detection with the IMAQ MagicWand VI bounded by your ROI boxes to produce the mask. It will fill to the edges of your region (either inside or outside your edge). You can then either use that as a mask or just count the pixels as a percentage of the area.

Thanks for the suggestion, I'll mess around with it and report back!

Can you tell us a bit more about what your desired measurement is? Are you just trying to get the area of the white stuff? Usually, you want to make this work as easy as possible for the software (crap in crap out principle) so you want to control the lighting and have a fixed ROI. Secondly you might want to use an auto threshold method so that it dynamically changes if the lighting control isn't perfect. Third, you'll notice the top of your image is much darker than the bottom. Your eyes are really good at subtracting shadows. Here's an example illusion based on that effect. You'll need have a different threshold for different parts of the image (preferably a gradient) to compensate for this.

    Thanks for the reply!  I have a couple different ROIs set up and I am measuring the amount of space inside the box that the "white stuff" occupies.  (see the image below)  I was a little vague about how I am actually doing the thresholding.  In short, I am not just using the threshold vi and hoping for the best.  I am trying to use an algorithm (using the Gaussian mixture model) that dynamically changes but like you said, with the lighting/contrast/brightness of the image always changing it does not always perform that well, whereas the edge detection seems to always find the correct edges.  

I suppose I was hoping I could use the edge detection as the base for some kind of mask or something...

Hello,

    I am having a bit of an issue applying a threshold to an image and getting reliable results.  I am thinking using edge detection prior to doing any other image processing could make this work...  but I am at a loss for how to implement it.  

    If you look at the image below you will see the root of my problem.  The top set of images and bottom are only a second or 2 apart but the threshold sees them differently, yet the edge detection seems to correctly detect the edges the same.  

I only care about the range of pixels that usually makes up the brightest part of the image (hence the thresholding)  but the low end of that range changes from frame to frame and I am left with an incorrect determination.  

My question is, does anyone know of a good way to use edge detection (or maybe some other method that I am not aware of) to help me with this problem?

I would like to try and upgrade my current CCD (pretty close to 640x480)  to a higher res model (1080p).  Here are my two requirements:

• It has to work LabVIEW/Vision software (could interface through GIG-E/IP or whatever)
• It has to fit inside of a tube about this size: (marker for scale)  http://i.imgur.com/9i8nPRE.jpg

The housing tube can be increased in size up to about a 1.25" diameter the tube runs back 2' until it opens up into an open space where we have a gigabit switch.  The camera could just have a telescoping lens or be small enough to fit in a tube that size with the cables running out the back of the tube.

I have been searching Hobby sites and small electronic sites/stores but nothing has caught my eye yet.  I am hoping someone here may be using some CCD (maybe for security reasons?) that does pretty close to what I need.

Thanks for any help!

What you're looking for is an analog frame grabber that supports DirectShow (which works out of the box with NI IMAQ like any webcam) or otherwise provides an API thats easy enough to integrate into LabVIEW.  

 

We've had good luck with ImperX and their analog frame grabbers designed for laptops.  They have DirectShow drivers and their own API which gives some additional control over acquisition (and a LabVIEW driver).  It doesn't look like your PC supports a Cardbus card, so thats probably out of the question.  

 

There are a number of inexpensive analog USB frame grabbers which might suit your needs.  We've tried some of them and have found all of them to have some quirks (nothing serious).  Most of these are pretty cheap, so you might as well try a few.  Since these will all appear like a webcam, they'll directly work with IMAQ... so write the code once, try them all.

 

We've been looking at another product from Pleora, but they have an analog frame grabber that works over GigE. 

Thanks for the response, I think ill do as you suggested and try a few different ones

I think you are after an analogue frame grabber rather than a trans-coder..

Something more akin to the boxed version of the VRmagic AVC-2 (I've never used it, but give it as an example)

Thanks for the response, I have been running some tests with my current setup (the axis video encoder) and the loss of image quality via compression may not be as bad as I had thought.  That being said, it will take a fair bit more testing before I will feel confident about that.  

Based on your suggestion I believe I may pick up one of these and run some comparisons.  There is still a desire for the video to be put on a network so I am still open to suggestions for how to accomplish that task. 

I recently had a project dropped into my lap and have had a tough time finding information about it on the web.  Here is a quick outline of my current issue.

I am trying to take in an analog video signal (640x480) and process the stream in LabVIEW/IMAQ/IMAQdx (end goal would be to have uncompressed video being processed).  I need to be able to have an uncompressed image to do calculations on. I am currently trying to achieve this by using an axis video server and converting the analog signal into a digital signal and finding the camera via an IP address (having networked video was requested as well...     Not a must though).

My understanding is that LabVIEW takes in the video stream as mjpeg (please correct me if I am wrong) and even at the lowest compression setting mjpeg streams are still compressed pretty heavily and use a lossy compression algorithm (again correct me if I am wrong) which will make doing any reliable image processing for me very difficult.

So my question is... Is there a better way to do this using any other hardware?  We will be putting the software on a pc like this, so I am unable to use pci/pci-e boards/cards but something through USB or Ethernet ports is fair game.

I really appreciate any help I can get!  

I am using LabVIEW 2011 with Vision 2011