finding submatrix and index

Question

Mohammad Golam Kibria 2013-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/76364-finding-submatrix-and-index

Hi I have the following matrix as two small sample matrix. I want to fill the matrix value zero with 1 between two diagonal 1.

I1=

I2=

I want to have my output as follows:

I1=

I2=

Thanks in advanced.

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Answer 1

Andrei Bobrov 2013-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/76364-finding-submatrix-and-index#answer_86017

编辑：Andrei Bobrov 2013-5-20

在 MATLAB Online 中打开

I1out = imdilate(I1,flipud(eye(min(size(I1)))));
I2out = imdilate(I2,eye(min(size(I1))));

ADD after Mohammad Golam Kibria's comment

s = size(I1);
d = 1-size(I1):size(I1,2)-1;
x = spdiags(I1(end:-1:1,:),d);
x1 = cumsum(x)&cumsum(x(end:-1:1,:));
I1out = full(spdiags(flipud(x1),d,s(1),s(2)));

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Mohammad Golam Kibria 2013-5-20

编辑：Mohammad Golam Kibria 2013-5-20

在 MATLAB Online 中打开

This does not work well. for example, if I1 =

   0     1     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     1     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0

then I1out = imdilate(I1,flipud(eye(min(size(I1))))); creates the following output:

-Inf     0     0     1     0     0     0     0     0     0
   0     1     0     0     0     0     0     0     0
   1     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     1     0     0
   0     0     0     0     0     1     0     0     0
   0     0     0     0     1     0     0     0     0
   0     0     0     1     0     0     0     0     0
   0     0     1     0     0     0     0     0     0
   0     1     0     0     0     0     0     0     0
   1     0     0     0     0     0     0     0     0

but I need the output as follows:

   0     1     0     0     0     0     0     0     0
   1     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
   0     1     0     0     0     0     0     0     0
   1     0     0     0     0     0     0     0     0
   0     0     0     0     0     0     0     0     0
could u please help me any more.

Image Analyst 2013-5-20

You would have to tell it which pairs to connect. Once you specify that, you can use my answer.

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Answer 2

Image Analyst 2013-5-20

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https://ww2.mathworks.cn/matlabcentral/answers/76364-finding-submatrix-and-index#answer_86023

You need to use Bresenham's Line Algorithm: http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm. If you have the Image Processing Toolbox, you can do that with imline(). Let me know if you want a demo of imline.

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Mohammad Golam Kibria 2013-5-21

yes, I need a demo. then it will be clear to me.

Image Analyst 2013-5-21

在 MATLAB Online 中打开

Here's the demo:

% Demo to write an ellipse and a line into the overlay of an image,
% and then to burn those overlays into the image.
%----- Initializing steps -----
% Clean up
clc;
clear all;
close all;
workspace; % Display the workspace panel.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
  end
end
% Display images to prepare for the demo.
monochromeImage = imread('pout.tif');
subplot(2, 4, 1);
imshow(monochromeImage);
title('Original Image');
subplot(2, 4, 2);
imshow(monochromeImage);
title('Original Image with ellipse in overlay');
subplot(2, 4, 5);
imshow(monochromeImage);
title('Original Image');
subplot(2, 4, 6);
imshow(monochromeImage);
title('Original Image with line in overlay');
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
set(gcf,'name','Image Analysis Demo','numbertitle','off') 
%----- Burn ellipse into image -----
% Create elliptical mask, h, as an ROI object over the second image.
subplot(2, 4, 2);
hEllipse = imellipse(gca,[10 10 50 150]); % Second argument defines ellipse shape and position.
% Create a binary image ("mask") from the ROI object.
binaryImage = hEllipse.createMask();
% Display the ellipse mask.
subplot(2, 4, 3);
imshow(binaryImage);
title('Binary mask of the ellipse');
% Let's try to add some text.  (Doesn't work)
% hText = text(50, 100, 'Line of Text');
% textMask = hText.createMask();
% binaryImage = binaryImage & textMask;
% imshow(binaryImage);
% Burn ellipse into image by setting it to 255 wherever the mask is true.
monochromeImage(binaryImage) = 255;
% Display the image with the "burned in" ellipse.
subplot(2, 4, 4);
imshow(monochromeImage);
title('New image with ellipse burned into image');
%----- Burn line into image -----
burnedImage = imread('pout.tif');
% Create line mask, h, as an ROI object over the second image in the bottom row.
subplot(2, 4, 6);
hLine = imline(gca,[10 100],[10 100]); % Second argument defines line endpoints.
% Create a binary image ("mask") from the ROI object.
binaryImage2 = hLine.createMask();
% Display the line mask.
subplot(2, 4, 7);
imshow(binaryImage2);
title('Binary mask of the line');
% Burn line into image by setting it to 255 wherever the mask is true.
burnedImage(binaryImage2) = 255;
% Display the image with the "burned in" line.
subplot(2, 4, 8);
imshow(burnedImage);
title('New image with line burned into image');