Demosaic VS ReturnedColorspace bayer

I have a 1920 x 1080 color camera that uses a bayer filter. I get the image with a NI camera link frame grabber.

If I get the image my taking a snap shot and applying a demosaic, the resulting image is correct.

If I try to set the .ReturnedColorspace = 'bayer', I get an image that has two additonal ghosts images (one above, one below) and the image appears to have an internlace misalignment.

http://i278.photobucket.com/albums/kk94/Jmgallag/Test1.jpg

Can anyone tell me why these give different results? Better yet, can anyone tell me how to set the videoinput properties to allow the ReturnedColorspace to work? I want the ReturnedColorspace technique to work since I would then be able to use the Preview command on the videoinput, vid.

clear all;
clc;

%%Demosaic
vid = videoinput('ni', 2, 'img0_Port1');
I = getsnapshot(vid);
J = demosaic(I, 'grbg');
figure;
imshow(J);
delete(vid);
clear vid;

%%Bayer Filter
vid = videoinput('ni', 2, 'img0_Port1');
vid.ReturnedColorspace = 'bayer';
vid.BayerSensorAlignment = 'grbg';
K = getsnapshot(vid);
figure;
imshow(K);
delete(vid);
clear vid;

[Walter Roberson]

Maybe asking for bayer makes the camera shake??

(I would add a wink to show I'm not serious, but... well, it _could_ happen.)

[Jeff]

It works fine when the camera resolution is incorrectly set at 1000 x 1000, so that rules out any physical vibration.

Answer 1

[Image Analyst]

Is the image monochrome? Is it possible that it's giving you the separate (raw) images? If it's color, maybe it's doing that but tinting the green image green, the red image red, and the blue image blue so that it looks color even though it's not - it's just the raw mosaiced image. Just guessing... Is it possible you could upload an image somewhere? Sorry I don't have a web cam on this computer or else I'd try your code.

[Jeff]

http://i278.photobucket.com/albums/kk94/Jmgallag/Test1.jpg

[Image Analyst]

Can you try another sensor alignment, such as rggb? Maybe you picked the wrong arrangement. See what happens.

[Jeff]

Thanks for the suggestion, but that only changed the color and does not fix the shifted images. Also I use the same arrangment for both above.

[Image Analyst]

I don't know. How did you even find out about setting those properties? I don't see them in the help for videoinput(). Each video adapter can have special properties that are specific/unique to each camera. Unless your adapter is the generic "winvideo" I suggest you contact your camera manufacturer for an explanation of those properties.

[Jeff]

I found those properties by watching the session log within the imaqtool toolbox. I haven't found much information on those properties either. I am using the same National Instruments adapter for both techniques.

To add to the confusion, I believe the colorspace method worked properly when the resolution was incorretly set to 1000 x 1000?

[Jeff]

I want the ReturnedColorspace technique to work since I would then be able to use the Preview command on the videoinput, vid. Is there a way to Preview or show realtime a demoasiced image?

Answer 2

[Jeff]

I found thru additional testing the problem with .ReturnedColorspace = 'bayer' is related to the aspect ratio being non-square. 1000 x 1000 - Works 1080 x 1080 - Works 1079 x 1080 - Problem 1920 x 1080 - Problem

Demosaic does not have issues with non-square aspect ratios.

A workaround is to use vid.ROIPosition = [420 0 1080 1080]; during preview(vid) and use the full ROI when collecting data.

I still don't know why the .ReturnedColorSpace can't handle non-square aspect ratios.