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function BlurredVideoCaptureDemo(filtertype, kwidth, deviceIndex)
% BlurredVideoCaptureDemo - Show application of image filters to videocaptured images.
%
% This demo shows how to apply 2D convolution kernels to a live video
% stream captured from an attached default camera. Convolution is not
% performed on the cpu by Matlab/Octave, but executed hardware-accelerated
% on the GPU for potentially much higher speed.
%
% Usage:
%
% BlurredVideoCaptureDemo([filtertype=1][, kwidth=11][, deviceIndex=0])
%
% 'filtertype' is optional and can be:
%
% 0 = None.
% 1 = Gaussian blur - This is the default.
% 2 = Prewitt operator.
% 3 = Unsharp operator.
% 4 = Sobel operator.
% 5 = Log operator.
%
% The filters are selected via the fspecial() function, and converted into
% proper convolution kernels. You may need the Matlab image processing
% toolobox or equivalent Octave package installed, for fspecial() to be
% available.
%
% 'kwidth' = Optional convolution kernel width in pixels. Defaults to 11.
%
% 'deviceIndex' = Optional index of the video capture device. Defaults to
% auto-selected default video source.
%
% Press any key to finish the demo.
%
AssertOpenGL;
screen=max(Screen('Screens'));
if IsOctave
pkg load image;
end
if nargin < 1 || isempty(filtertype)
filtertype = 1;
end
if nargin < 2 || isempty(kwidth)
kwidth=11;
end
if nargin < 3 || isempty(deviceIndex)
deviceIndex = [];
end
try
InitializeMatlabOpenGL;
win=Screen('OpenWindow', screen, 0);
% Initial flip to a blank screen:
Screen('Flip',win);
% Set text size for info text. 24 pixels is also good for Linux.
Screen('TextSize', win, 24);
% Build a filter kernel:
stddev = kwidth / 3;
switch(filtertype)
case 0
kernel = [];
case 1
kernel = fspecial('gaussian', kwidth, stddev);
case 2
kernel = fspecial('prewitt');
case 3
kernel = fspecial('unsharp');
case 4
kernel = fspecial('sobel');
case 5
kernel = fspecial('log');
end
if filtertype > 0
% Build shader from kernel:
shader = EXPCreateStatic2DConvolutionShader(kernel, 3, 3, 0, 1);
else
% No filtering requested: Select fixed-function pipeline
shader = 0;
end
% Open video capture device:
grabber = Screen('OpenVideoCapture', win, deviceIndex);
% Start video capture:
Screen('StartVideoCapture', grabber);
count = 0;
t=GetSecs;
% Repeat until keypress or timeout of 10 minutes:
while ((GetSecs - t) < 600) && ~KbCheck
% Wait for next video image:
tex = Screen('GetCapturedImage', win, grabber, 1);
% Valid?
if tex > 0
% Draw new video texture from framegrabber.
Screen('DrawTexture', win, tex, [], [], [], [], [], [], shader);
Screen('Close', tex);
% Show it:
Screen('Flip', win);
end
count = count + 1;
end
telapsed = GetSecs - t
% Stop and close video source:
Screen('StopVideoCapture', grabber);
Screen('CloseVideoCapture', grabber);
% Close down everything else:
sca;
avgfps = count / telapsed
catch
sca;
psychrethrow(psychlasterror);
end
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