VI modifies the source image

[Vladimir Drzik]

Hi guys,

In the help description of many image processing VIs, there is this particular note:

"This VI modifies the source image. If you need the original source image, Create a copy of the image using IMAQ Copy before using this VI."

Is this really true even if you connect a separate image to the "Image Dst" connector? I have tried it with the "IMAQ Convolute" VI and I can't see any difference been made to the source image. Actually, in time critical applications, it would be quite a terrible waste of time having to copy the original image every time I want to run a processing VI and still keep the original image.

Is there any document describing deeper how IMAQ VIs work at low level? Besides my current question, I would like to know also the details about memory allocation etc...

Vladimir

[crelf]

What the documentation should say is "If you do not wire in a destination image, this VI modifies the source image. If you need the original source image, create a copy of the image using IMAQ Copy and wire the copy in as the destination before using this VI."

[Vladimir Drzik]

Thanks for the explanation. This is quite a misleading statement in the documentation...

Anyway, I still wonder why this statement does not appear at all processing VIs. Take e.g. IMAQ CannyEdgeDetection, there is no such note there, though the VI works the same way.

Still I would appreciate some more insider info... Let's assume that we are running the processing VIs on one image only (Dst unwired). Some processing algorithms require a separate temporary image to be allocated during the processing, some don't. Where can you get the information about which ones do and which ones don't? This is a critical question if you are trying to optimize the application for speed.

Vladimir