Could I change IMAQ image display property in subvi?

[Anne Zuo]

Hi,

I have a IMAQ image display on FP, and I change its properties by property nodes. The code works fine.

Now I select those code and want to create a subvi, and it refuses to do it.


Why?      Thanks for any help.

Anne

[GuenterMueller]

Hi Anne.

It might be a LabVIEW bug. I see the same (as you say) in LV8.5.1 and NI Vision 8.5.0: Selecting an Image Display Control's Property Node on the block diagram and using Edit>>Create SubVI results in no action by LabVIEW.

Doing the same in LV8.2.1 results in a (broken) SubVI with a Control RefNum for which LabVIEW reports the error "Control requires an external library" ...
Maybe you can circumvent this by creating a SubVI that takes a Control RefNum as a parameter and use "To More Specific Class" to typecast it to an ImageControl. Now you can wire Property Nodes as expected.

Can anyone put some light on this?
Regards, Guenter

[Anne Zuo]

Hi Guenter,

I got a way around it, convert the image reference to variant, and in subvi convert it back to image reference. 

It works.

Anne

[GuenterMueller]

Sorry for this post!


Message Edited by Guenter Mueller on 05-01-2008 01:44 AM

[Lefi]

I've found another, perhaps more straight on, work-around to this annoying bug. Instead of converting the image display reference to a variant, a generic control reference can be used as input to the sub-VI and then converting it to a specific image control reference with "To More Specific Class" with an image control reference constant. This constant you can create by first dropping a dummy image display on the front panel, creating a reference to the image display and then creating a constant to this reference. Then you can delete the front panel image.

Doing this, you can connect the image display reference direct to the sub-VI.