MATLAB: Preview video feed using surf

Question

Hi all,

I've got a gige camera and using Matlab to create a gui with some controlling functions/processing buttons for the camera images.

Using the following

Image = preview(VidObj);
ExtractedFrame = Image.CData;

I've been able to get the video feed to plot as 3D data which is what I'm looking for.

However, the preview window (small window, also showing the video stream) is always present and tends to be dominant in activity.

This is OK for the most but I think that because it's always visible (it's the active window on top of my gui figure), it's taking away control from my GUI.

I've added sliders in to control the viewing angle (which would be nicer to use the "surf" rotate by clicking and spinning the image, but again it works for what I need.

Where I'm struggling is adjusting camera exposure – it's presently set up as a

uicontrol('Style','edit', ...)

which is ideally how I'd like it, but the VideoPreview window always keeps the focus, so I can't actually highlight the exposure time to 'edit' the value (can't get the GUI active for long enough)

But to have the gui with additional buttons and controls is where I'm headed, and using preview(VidObj) only lets this be a 2D image (where I'd like to see peaks as the attached screenshot shows)

One can also see the controls I have – change colormap ('rainbow' = jet), control min & max Z, exposure, then the sliders to control the 'view' of the surf plot of the image.

As I'm also doing more image processing, I can export the image displayed (at the bottom), find camera values above certain Z (peak detection) and apply Z thresholding

Z(Z<Thresh)=0

by pressing the buttons at the bottom left of the GUI

I'm planning to add more, but tidying the surf(Image) from preview(VidObj) will probably be the quickest way to handle this (and further issues?!)

I include my main code also which is handling the camera acquisition

function DisplayCameraFeed(~, ~)
    VidObj = videoinput('gige');
    VidObj.SelectedSourceName = 'input1';
    [~] = preview(VidObj);        % Important to initialise camera!
    while GUI_Handles.Toggle_MAIN.Value
      NthFrame = NthFrame + 1;
	%% This section gets the camera settings
	VideoProperties					= get(VidObj);
	CameraProperties				= getselectedsource(VidObj);						% Added 20191204; to access features like camera exposure, etc
%	VideoProperties.Previewing		= 'off';    % TRIED TO REMOVE THE DOMINANT PREVIEW WINDOW, didn't work!
	CameraProperties.ExposureTime	= str2double(GUI_Handles.Text_SetExposure.String);	% Extract the handle (it's a string) from the exposure
%% Now we're ready to get the image from the camera, and do any potential processing
	Image = preview(VidObj);
	ExtractedFrame = Image.CData;
	% Check that surf/mesh will be able to display the image OK (greyscale)
	switch size(ExtractedFrame, 3)
        case 1	% No change needed
        case 3	% Make RGB2Gray
	    ExtractedFrame = rgb2gray(ExtractedFrame);
	  otherwise	% Oh dear!
	    keyboard;
	end
	GUI_Handles.GlobalCell{2, 4} = ExtractedFrame;    % Store image
	if GUI_Handles.Toggle_Slicing.Value		% Only want the sliced image above the threshold
	    Toggle_Slicing;
	    ExtractedFrame = GUI_Handles.GlobalCell{2, 4};
	end
	%% Displaying of the image.
	surf(flipud(ExtractedFrame));	% Matlab flips for surf plot
	shading flat;
	axis tight;
	SetColorMap;
	SliderCheck;
	AXES				= gca;
	AXES.Position		= [0.25, 0.25, 0.7, 0.7];
	AXES.XAxis.Visible = 'off';
	AXES.YAxis.Visible = 'off';
	AXES.CLim			= [GUI_Handles.Slider_Z_Min.Value,			GUI_Handles.Slider_Z_Max.Value];
	AXES.ZLim			= [GUI_Handles.Slider_Z_Min.Value,			GUI_Handles.Slider_Z_Max.Value];
	AXES.View			= [GUI_Handles.Slider_Angle_Azimuth.Value,	GUI_Handles.Slider_Angle_Elevation.Value];
	AXES.XLabel.String	= sprintf('X');
	AXES.YLabel.String	= sprintf('Y');
	AXES.XGrid			= 'off';
	AXES.YGrid			= 'off';
	AXES.ZGrid			= 'off';
	%% Add peak detection:
	drawnow;
	hold on;
	Toggle_PeakDetector;
	% drawnow;
	hold off;
    end
stoppreview(VidObj)
end

Thanks for your help 🙂

Answer 1

Sorted - manual setting, see line around 10 below. Just needed to do some more digging for anyone interested.

The below allows me to debug on macbook pro (facetime camera) and use on linux with the gige camera. Frame rate a bit shower than we'd like (6fps) but very usable.

SOLUTION:

function DisplayCameraFeed(~, ~)
		NthFrame = 0;
		if ismac
			VidObj	= videoinput('macvideo');	% 20191204 - added Mac camera use. This should allow debugging of all features (including exposure, etc)
		else
			VidObj	= videoinput('gige');
		end
		VidSrc		= getselectedsource(VidObj);
		triggerconfig(VidObj, 'manual');		% 20191205; https://uk.mathworks.com/help/imaq/examples/acquiring-a-single-image-in-a-loop.html
		start(VidObj);
		while GUI_Handles.Toggle_MAIN.Value
			if ~mod(NthFrame, 3)
				StartTimer		= tic;
			end
			if ~contains(VidObj.Name, 'macvideo')
				ExposureTime		= str2double(GUI_Handles.Input_SetExposure.String);
				VidSrc.ExposureTime	= ExposureTime;
			end
			NthFrame		= NthFrame + 1;
			ExtractedFrame	= getsnapshot(VidObj);
			switch size(ExtractedFrame, 3)
				case 1	% No change needed
				case 3	% Make RGB2Gray
					ExtractedFrame = rgb2gray(ExtractedFrame);
				otherwise	% Oh dear!
					keyboard;
			end
			if GUI_Handles.Toggle_Slicing.Value		% Only want the sliced image above the threshold
				GUI_Handles.GlobalCell{2, 4} = ExtractedFrame;
				Toggle_Slicing;
				ExtractedFrame = GUI_Handles.GlobalCell{2, 4};
			end
			%% Displaying of the image.
			SetColorMap;
			if GUI_Handles.Slider_Angle_Elevation.Value == 90
				imagesc(ExtractedFrame);
				AXES			= gca;
			else
				surf(flipud(ExtractedFrame));	% Matlab flips for surf plot
				shading flat;
				axis tight;
				AXES			= gca;
				AXES.ZLim		= [GUI_Handles.Slider_Z_Min.Value,			GUI_Handles.Slider_Z_Max.Value];
			end
			SliderCheck;
			AXES.Position		= [0.25, 0.25, 0.7, 0.7];
			AXES.XAxis.Visible = 'off';
			AXES.YAxis.Visible = 'off';
			AXES.CLim			= [GUI_Handles.Slider_Z_Min.Value,			GUI_Handles.Slider_Z_Max.Value];
			AXES.View			= [GUI_Handles.Slider_Angle_Azimuth.Value,	GUI_Handles.Slider_Angle_Elevation.Value];
			AXES.XLabel.String	= sprintf('X');
			AXES.YLabel.String	= sprintf('Y');
			AXES.XGrid			= 'off';
			AXES.YGrid			= 'off';
			AXES.ZGrid			= 'off';
			SetColorMap;
			CBAR 				= colorbar;
			drawnow;
			%% Add peak detection:
			if GUI_Handles.Toggle_PeakDetector.Value
				hold on;
				Toggle_PeakDetector;
				hold off;
			end
			if ~mod(NthFrame, 3)
				GUI_Handles.GlobalCell{2, 4} = ExtractedFrame;
				TimeTakenForNFrames = toc(StartTimer);
				TimePerFrame 		= TimeTakenForNFrames / 3;
				FrameRate			= 1 / TimePerFrame;
				set(GUI_Handles.Label_FrameRate,	'String',sprintf('Frame Rate = %0.2f', FrameRate));
			end
		end
		stop(VidObj);
	end