LabVIEW 8 Save JPEG Error (blank/gray screen)

[elkapitann]

I run a program in LabVIEW 8.20 where I save many front panel images to jpeg files. Occasionally, rather randomly, the image saved is just a blank gray screen. The dimensions of the blank screen are equal to the demensions of the front panel I am expecting to see saved. I use the Method --> Front Panel, Get Image...then wire it into the provided "Write JPEG File.vi"

I use the option of "Visible area only" as false.

I don't think I am doing anything incorrectly, because the image is saved 90% of the time. It's the other 10% that is really hindering me, because often the plots I want images of take a great deal of time to acquire.

Any help would be appreciated...

[zou]

Can't reproduce your problem here.

Try to add a delay between plot update and Get Image.

[elkapitann]

It isn't that the panel isn't updated, it's that it is just a gray screen, no image at all. I'll see if I can write a simpler program to repeat the error and attach it to this thread. It is also very random, so it can take awhile to reproduce. Others in my programming group have seen this also.

Thanks for replying however...

[TCPlomp]

LV 8.0(.1) have a bug that saving/plotting tranparent areas will become gray, solved for LV 8.2

Ton

[GerdW]

Hi captain,

this will not solve the problem, but it's worth mentioning: for frontpanels (when there are no big colorful graphics) PNG should be the better format for saving images!

[James_Happe]

I am having the same problem as elkapitann.  Someone stated that this problem has been fixed in 8.20, but elkapitann said that was what he was running. Can it be confirmed that this problem has been fixed in 8.20?  Is there a fix for those of us stuck running 8.0?

Thanx,

James

[Devin_K]

Hi James,

I was unable to reproduce the behavior that you and elkapitann were seeing in LabVIEW 8.0.  I saved 500 screenshots of a front panel with a randomized graph, and they all appeared correctly.  What operating system are you using?  My tests were done on Windows XP.

Does this behavior always occur, or is there a particular VI that causes the problem?  If you attached your VI, I could test it to see if I can reproduce the behavior.

If you haven't already, it would be worthwhile to try the suggestions above.  Does the problem remain if you add a delay or use .PNG files instead of .JPG?

Regards,

[elkapitann]

I determined one way to re-create the problem. Similar to what you stated above, loop a random graph generator to a jpg file, then minimize the front panel of the vi while running. Or, have the front panel minimized and launch from back panel. I don't think this is the only way to cause this, as it's happened to me unattended, but this worked for me.

[Devin_K]

Thanks for the update elkapitann.  I was able to reproduce the behavior in LabVIEW 8.2 and 8.5.  However, it seems that what is actually happening is that the front panel is being shifted in the image.  If you had a small front panel, or the image was shifted by a large amount, the image would appear blank/gray, as you described.

R&D is aware of the issue, and is working to have it fixed in a future version of LabVIEW.  In the meantime, one potential workaround would be to manually shift the front panel when it is minimized so that the images appear correctly.  On my machine, the image is always shifted 46 pixels up.  Have a look at the attached code to see how to compensate for this.

I hope that that helps, and I apologize for any inconvenience this has caused you.

Edit: I should also note that in order to get this to work, I needed to set "Visible Area Only" to True.

Regards,



Message Edited by Devin_K on 12-31-2007 03:55 PM

[James_Happe]

Thank you for your help.  I just don't let the user minimize or resize the window.  Time will tell how well this will work.