how to apply the result of bwboundaries() output ?

This is the code.

%%%%%%Code begins %%%%
boundaries = bwboundaries(img);
NumOfBoundaries = size(boundaries, 1);

[x y t]= size(rgbImage);

ZeroPlate = redChannel == 0;
for k = 1 : NumOfBoundaries 
thisBoundary = boundaries{k};

%%%%%I want to set Value '1' to 'ZeroPlate' co-%%%ordination given in 'thisBoundary' %%%%%%%%

%%%%%---------------the code goes here------------------%%%%

%%%%%end %%%%%

end

I want to set value '1' to the ZeroPlate (which is red-channel of the given image in which the pixel values are all zeros) according to the co-ordination obtaining from the values of 'boundaries' variable. How to do this ?

Answer 1

[Image Analyst]

Try this:

%%%%%%Code begins %%%%
boundaries = bwboundaries(img);
NumOfBoundaries = size(boundaries, 1);

% Get size.  
% Note: it is NOT NOT NOT [x,y,numColors] = size(rgbImage) as you had it.
% rows is y, NOT x.  But actually this line is not needed.
[rows, columns, numberOfColorChannels]= size(rgbImage);

ZeroPlate = redChannel == 0;
for k = 1 : NumOfBoundaries
  thisBoundary = boundaries{k};
  % Set Value '1' to 'ZeroPlate' 
  % coordinates given in 'thisBoundary'
  x = thisBoundary(:, 1);
  y = thisBoundary(:, 2);
  for index = 1 : length(x)
    % Get row and column.
    row = y(index);
    column = x(index);
    % Set that row and column = true = 1.
    ZeroPlate(row, column) = true;
  end
end

[Piyum Rangana]

Thanks a lot sir, Actually I have one thing to understand in the answer. I n the final answer 'ZeroPlate' does not came with same rows and columns as the initial image. And also I cannot understand why we need this line

ZeroPlate(row, column)=true;

Actually why we cannot directly write [row column] = ZeroPlate ?

I think that if I use

row    = x(index);
column = y(index);

The issue seems like OK.

[Image Analyst]

I set it equal to true because ZeroPlate is a binary image and you said you want the value to be 1 (true).

Actually you're right sort of - I switched x and y. I thought bwboundaries returned (x,y) coordinates but it doesn't - it returns (row, column) which is (y, x). So the correct code should be:

for k = 1 : NumOfBoundaries
  thisBoundary = boundaries{k};
  % Set Value '1' to 'ZeroPlate' 
  % coordinates given in 'thisBoundary'
  x = thisBoundary(:, 2);
  y = thisBoundary(:, 1);
  for index = 1 : length(x)
    % Get row and column.
    row = y(index);
    column = x(index);
    % Set that row and column = true = 1.
    ZeroPlate(row, column) = true;
  end
end

[Piyum Rangana]

Thanks a lot for the support.