Video frame selection

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Colm
Colm el 16 de Nov. de 2011
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

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David Tarkowski
David Tarkowski el 16 de Nov. de 2011
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;
  3 comentarios
Colm
Colm el 23 de Nov. de 2011
but the variable 'diffFrame' doesn't contain any negitive values?
Image Analyst
Image Analyst el 23 de Nov. de 2011
You need to cast as single() or double() because uint8 doesn't allow any values outside 0-255.

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