Boundary Extraction Issue Using Image Restoration Techniques

Hi, I'm working on extracting boundary points from an image, but the output appears inverted. How can I correctly extract boundary points so the image restoration matches the original orientation? Here's my current MATLAB code:

clear all;
img = imread('parol.png'); % Replace with your image file
grayImg = rgb2gray(img); % Convert to grayscale
bwImg = imbinarize(grayImg); % Convert to binary image

% Invert the binary image if necessary
bwImg = imcomplement(bwImg);

% Fill holes in the binary image
bwImg = imfill(bwImg, 'holes');

% Get boundary points
boundaries = bwboundaries(bwImg);

% Extract the main boundary points
boundaryPoints = boundaries{1};

% Plot the boundary points
figure;
subplot(1,2,1)
imshow(img);
subplot(1,2,2)
plot(boundaryPoints(:,2), boundaryPoints(:,1), 'r', 'LineWidth', 2);
hold off; 
daspect([1 1 1]);

Thanks!

Answer 1

[Image Analyst]

After you call plot, do this:

axis('on', 'image');

or you can do

axis ij

[Yamina chbak]

okey

[Image Analyst]

It doesn't look any different. Are you sure you put in the code I gave you?

The other option is

axis xy

but that is what plot normally does - plot x vs y so the origin is at the bottom left. Doing axis ij puts the origin at the top left, effectively flipping the plot top to bottom. But use whichever gives you the orientation you want.

Attach 'parol.png' if you still need more help.

[Yamina chbak]

Okay @Image Analyst, I made sure to include the code you mentioned, and here is the result:

However, it is not exactly as shown in the attached 'parol.png'. The problem seems to be with the orientation.

[Image Analyst]

"I made sure to include the code you mentioned" <= no, I don't think so. Here is what I suggested:

clear all;
img = imread('parol.png'); % Replace with your image file
grayImg = rgb2gray(img); % Convert to grayscale
bwImg = imbinarize(grayImg); % Convert to binary image
% Invert the binary image if necessary
bwImg = imcomplement(bwImg);
% Fill holes in the binary image
bwImg = imfill(bwImg, 'holes');
% Get boundary points
boundaries = bwboundaries(bwImg);
% Extract the main boundary points
boundaryPoints = boundaries{1};
% Plot the boundary points
figure;
subplot(1,2,1)
imshow(img);
axis('on', 'image')
subplot(1,2,2)
plot(boundaryPoints(:,2), boundaryPoints(:,1), 'r', 'LineWidth', 2);
axis('ij', 'equal')

[Yamina chbak]

Okay, I understand what you're trying to do, but I still find the image is inverted and clear on the y-axis; the numbers should go from bottom to top. Anyway, I will input an inverted image to make the output appear correct.

Thank you @Image Analyst for your help.

[Image Analyst]

Not sure what you're saying. Both the images have the same orientation, even though one is an image and one is a plot. Perhaps you're confused about the location of the origin for images and plots.

For images and arrays, the top row is row 0 and that is the origin, and the row numbers on the y axis increase as they go from the top left of the axes to the bottom left of the axes.

For plots, which have (x,y) plot coordinate points, the origin (0,0) point, is at the lower left, and the y axis tick labels on the y axis increase as they go from the bottom left of the axes to the top left of the axes.

That's just the convention everyone uses. MATLAB does give you functions to make it appear differently if you don't like the way the convention appears, and I've showed you some of those.

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