Hello,
I have been struggling on a problem for a couple of days now, and I am looking for a bit of help on a "simple" aspect of NI LabVIEW and NI Vision.
First, I will just give the context of my problem : I have a camera (set on a microscope) which is grabbing images from my sample. I need to record the raw images directly obtained by the camera (so without any pre-processing) because I have some routines of post-processing to apply on them. However, while and in between recording, I need to move in my sample and either look for event or track them (manually). So I need in the same time to pre-process the signal and display it, so I can have a good visualization of the sample.
For this, I am required (by the different natures of the samples I usually work with) to switch between two types of pre-processing for visualization: (i) correction by the subtraction of a constant background image (taken in a blank part of the sample). This part is already done and working perfectly fine. (ii) correction by group averaging on N frames. And this is the part I have trouble with.
So the second type of correction is pretty simple in its description: (1) I collect N frames, (2) I average them (using the IMAQ Compute Average Image.vi so far), (3) and then I take the N+1th (raw) frame and divide it by the average computed just before. Then I restart from (1).
Using the examples and other topics ( for example here ), I have managed to make this running with a For Loop and a Ring acquisition.
The problem is that, until the foor loop is completed on the N frames, the program does not do anything else. Which means it does not display or record the raw frames anymore. So my frame rate becomes (true FPS) / N, which is terrible for my application.
I have tried several ways to do it, by adding pixels values of images and finally dividing them by N (with IMAQ Add.vi and so), but it does not work at all (I only got a black screen on display).
I feel like I could do this with a very simple way, by inserting directly the N IMAG Images in an array, processing it with the IMAQ Compute Average Image.vi on the Nth frame and re-initialising the array at the end. After all, IMAQ Compute Average Image.vi is designed to work with Image array (cf Online description). However, I cannot find anyway to create such array of images than by using a For loop (which is slowing my acquisition down drastically).
So how can one create an IMAQ image array without using a For loop (such as in the example given above)? Could it be done with a While loop and a shift register for example, so the display and acquistion of my raw images are not impacted by the group averaging?
Best
PS: I do not include a VI because I don't think it would be really relevant regarding my question, but I can send my test one if needed
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