The IMAQ histogram does not work on SGL images

[10Degree]

I have found that the IMAQ Histogram or Histograph VI’s do not work on single precision (SGL) images.  The histogram generates a starting value and an incremental value which seem to correlate to the first bin in your bin range that actually contains “counts” rather than the first bin in the range.  The problem is obvious when a Histograph is wired to a waveform graph.

The attached VI compares the output of the IMAQ histograph vi and the LabVIEW general histogram vi.  The general histogram works correctly.  The vi generates and analyzes an image of Gaussian noise.

Can you please verify that this is indeed a bug with the IMAQ histogram algorithms or advise me in the correct use of the IMAQ histogram vi?

Thanks,

-cb

[mfitzsimons]

Looks good to me.  Is this what you expect?

Matt

[10Degree]

Matt,

I might be looking at a version problem - I get different results on another machine.  Can you tell me what version of IMAQ vision you are running?

-cb

[mfitzsimons]

LabVIEW 8.0.1

IMAQ 3.5.1

Vision 8.0.0

Good Luck!

Matt

[David S.]

Hi 10degree -

If you have a different version of the software than Matt, could you post a similar screenshot to his with the output you see?  If there's a difference, I can test it out and investigate it for you.

[10Degree]

David,

I found that the histogram worked correctly on IMAQ 7.1.1, but did not work on version 7.1.0.  I have attached a screen shot of the application from the incorrect 7.1.0 histogram.  The histogram should be centered around zero, but is shifted to the right.

As an aside, I also had problems with the IMAQ Quantify.vi in another application.  I was using it to compute pixel statistics (mean, min, max, etc) in the "Global Report" output cluster.  It did not compute the statistics correctly and I ended up using the IMAQ Histogram.vi to derive those. 

Please let me know what you find!

-10

[David S.]

Hi 10Degree -

I can't reproduce the problem in Vision 7.1.0 and LV 8.0  Which version of LV are you using?