Keep Overlays on IMAQ

[TimT2006]

Hi there,

I am using the Vision toolkit to show recorded frames with a camera.

To make some analysis I put some ROI's onto the image. Moreover I do also use overlays.

If I am updating the image the overlay disappears. How can I keep the overlays and Roi's on the image while updating it?

Thank you in advance!

[GuenterMueller]

I draw any overlay after an image has been acquired. Usually, any image acquisition clears the overlay.

You could create another image which can take a backup copy of your overlay, run one image acquision, and then apply the backup copy.

[Topper_Harley]

Hi Tim,

what you experience is caused by the fact that IMAQ images do NOT follow data flow. This concept is quite uncommon in LabVIEW. There is only a single image buffer which is referenced and when this buffer is written to by a new acquisition, the old image is lost anywhere in your VI.

You can create multiple image buffers and keep multiple images, as Guenter suggested. Of course, it is possible to add the overlay to each newly acquired image.

Is re-writing the overlay with each acquisition an option for you?

Regards, Topp

[frog7]

How would I do this in labview? I need to take a series of images and located an ROI point based on saved coordinates in an Excel file.

[Topper_Harley]

frog7, have a look at these examples:

Image Acquisition Functional Global Variable (IMAQ or IMAQdx)

https://decibel.ni.com/content/docs/DOC-8667

Create New Image from User Selected ROI

https://decibel.ni.com/content/docs/DOC-8667

Also, have a look at "IMAQ Sequence.vi". This is meant to acquire a finite series of images.

[frog7]

These two addresses are for the same location. I want to open an image and select an ROI based on pixel coordinates I have stored in another file. I do not want to select an ROI on screen and save it again.

[Christian Mergl]

Honestly I don't really know a reason why your overlays should disappear,

but as an alternative to the suggestions before you could use "IMAQ Merge Overlay" to merge them down to the image. But keep in mind that the imagetype will change to U32 RGB then!

Christian

[Topper_Harley]

My bad.

 

Image Acquisition Functional Global Variable (IMAQ or IMAQdx)

https://decibel.ni.com/content/docs/DOC-14767