Video frame selection

I'm sure this has an easy answer but if I set a trigger to capture 2 frames how can I independently assign '[vid,1]' and '[vid,2]' as variables? My reason for doing this is to subtract one image from another (and then divide the qualitative noise. 2 to the power of 0.5, Dark current calculations).

vid = videoinput('gige', 1, 'Mono16');
src = getselectedsource(vid);
vid.FramesPerTrigger = 2;
start(vid);

Thanks

Answer 1

[David Tarkowski]

There are a number of ways to this that are roughly equivalent. By default the GETDATA command returns N frames where N is equal to the value of the FramesPerTrigger property when GETDATA is called. You could do something like:

data = getdata(vid);
diffFrame = data(:,:,:,2) - data(:,:,:,1);

You can also specify the number of frames that GETDATA should return:

image1 = getdata(vid, 1); % Here 1 is the number of frames to return
image2 = getdata(vid, 1);
diffFrame = image2 - image1;

Of course, you could also do:

data = getdata(vid); % Get both frames
image1 = data(:,:,:,1); % The first frame
image2 = data(:,:,:,2); % The second frame
diffFrame = image2 - image1;

[Colm]

Thanks.

I just need the diffFrame line.

[Colm]

but the variable 'diffFrame' doesn't contain any negitive values?

[Image Analyst]

You need to cast as single() or double() because uint8 doesn't allow any values outside 0-255.