getting error in lane detection

I am not familiar with matlab. i had used your tutorial video no 6 and getting error in following statement

lanes=findlanes(B,h,stats);
hold off;

and i am getting following error

??? Undefined function or variable
'stats'.

can you help me resolving following error

[Walter Roberson]

This is possibly a reference to http://www.mathworks.com/matlabcentral/fileexchange/41989-matlab-for-c-c++-programmers

Answer 1

[Walter Roberson]

Look at http://www.mathworks.com/matlabcentral/fileexchange/41989-matlab-for-c-c++-programmers/content/MATLAB_C_DemoFiles_makezip/1-MATLAB_Intro_Lanes/lanemarkings.m

and see the lines of code there:

% Extract statistics
stats = regionprops(L,'MajorAxisLength','MinorAxisLength');

You do not appear to have done that before calling findlanes()

[mustafa wala]

I am not satisfied with your answer. I had listed codes which I had used in this. You can see it below.

%%Lane Marking Identification  
%%Read image  
street = imread('street1.jpg');  
%%Display image  
figure;  
gray(256);  
imagesc(street1);  
%%Scale image  
scaled=street1*1.05;  
image(scaled);  
%%Threshold  
level=211;  
binary = scaled>level;  
imagesc(binary);  
%%Remove the noise  
binary = bwareaopen(binary,100);  
imagesc(binary)  
hold on 
%%Find the boundaries of objects  
[B,L] = bwboundaries(binary(:,:),'noholes');  
h = zeros(1,length(B));
% Plot boundaries  
for K=1:length(B)  
    boundary = B{K};  
    h(K)=plot(boundary(:,2), boundary(:,1), 'g','LineWidth', 2);
end  
% Extract statistics  
stats = regionprops(L,'MajorAxisLength','MinorAxisLength');  
%%Find lanes and delete non-lane objects  
lanes=find_lanes(B,h,stats);  
hold off;

Can you correct it, and give me the answer with the reasons?

[Walter Roberson]

I will need to see the complete traceback of the error message. Your Question refers to a line which invokes findlanes() but your code here refers to find_lanes(), a different routine. Possibly you are using a find_lanes() that invokes findlanes() so the problem might be in your find_lanes() routine, whatever content it might happen to have.

Please show the output of

which -all find_lanes
which -all findlanes

[Image Analyst]

I'm not satisfied with your comment, mustafa. Please attach 'street1.jpg' so people can actually run your code.

Answer 2

[Image Analyst]

You say that it's saying stats is undefined. So change this code

% Extract statistics  
stats = regionprops(L,'MajorAxisLength','MinorAxisLength');  
%%Find lanes and delete non-lane objects  
lanes=find_lanes(B,h,stats);

to this code:

% Extract statistics  
stats = regionprops(L,'MajorAxisLength','MinorAxisLength');  
whos stats
which find_lanes
whos find_lanes
%%Find lanes and delete non-lane objects  
lanes=find_lanes(B,h,stats);

and tell me what it says in the command window.

[mustafa wala]

i tried your above statements and it gives following output in command window

'find_lanes' not found. ??? Undefined function or method 'find_lanes' for input arguments of type 'cell'.

[Oghenemine Henry]

I always get this error message when trying to run the code. Please how do I correct this Error using bwboundaries Expected input number 1, BW, to be two-dimensional.

Error in bwboundaries>parseInputs (line 159) validateattributes(BW, {'numeric','logical'}, {'real','2d','nonsparse'}, ...

Error in bwboundaries (line 128) [BW, conn, findholes] = parseInputs(varargin{:});

Error in lanemarkings (line 21) [B,L,N]=bwboundaries(binary, 'noholes');

[Image Analyst]

Your BW is most likely a true color RGB image rather than a binary (logical) image. What does this say:

whos BW

[Oghenemine Henry]

nothing appears when I type

whos BW

[Image Analyst]

It looks like BW is the name given by some internal functions. It looks like you called it "binary" so what does whos binary show? It probably shows that it's a color image not a "logical" binary image.

[Oghenemine Henry]

whos binary Name Size Bytes Class Attributes

binary      568x962x3            1639248  logical

[Image Analyst]

binary is a 3-D volumetric image, like you're dealing with CT or MRI images or something. I don't think this should be. You should convert street to a grayscale image before you threshold it at 211.

From street, or street1, whatever you called the variable, which color channel do you want to use? Or do you want to take a weighted average?

if ndims(street)
  street = rgb2gray(street);
end