MATLAB: Identify a boundary in an image (matrix form)

image analysisimage processingImage Processing Toolbox

Hi,

i have a matrix with the size of 25*20*10 (lon*lat*time). I would like to find the boundary of the image. Any ideas on how to do that?Here is part of the matrix (25*20*1):

Best Answer

One way that works for multiple regions in the 2-D image "m":

validData = ~isnan(m); % Map of valid (non-nan) locations of matrix m.
boundaries = bwboundaries(validData);
imshow(m, [], 'InitialMagnification', 1000); % Display this matrix.
axis('on', 'image'); % Display tick marks.
hold on; % Don't let boundaries blow away image because we want to plot them over the image.
for k = 1 : length(boundaries)
    thisBoundary = boundaries{k}; % Get this particular boundary.
    plot(thisBoundary(:, 2), thisBoundary(:, 1), 'r-', 'LineWidth', 2); % Plot it.
end

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MATLAB: Assigning color to gray image

I'd just use colormap and not mess with contours unless you know what you're doing and what you want. To pseudocolor a grayscale image an leave it as grayscale but display it as colored:

imshow(grayImage);
colormap(jet(256));
colorbar;

To convert a grayscale image into a true color RGB image and display the RGB image instead of the pseudocolored image:

rgbImage = ind2rgb(grayImage, jet(256));
imshow(rgbImage);

You don't use color bars with RGB images.

MATLAB: I have RGB (MxNx3) image and a binary mask (MxN). I want to place this mask over the RGB such that a line should be shown along the shape of the mask on the RGB image.

Call bwboundaries() then plot

boundaries = bwboundaries(binaryImage);
numberOfBoundaries = size(boundaries, 1);
hold on;
for k = 1 : numberOfBoundaries
  thisBoundary = boundaries{k};
  plot(thisBoundary(:,2), thisBoundary(:,1), 'r-', 'LineWidth', 2);
end
hold off;

Best Answer

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MATLAB: Assigning color to gray image

MATLAB: I have RGB (MxNx3) image and a binary mask (MxN). I want to place this mask over the RGB such that a line should be shown along the shape of the mask on the RGB image.

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