MATLAB: Can a particular portion of an image be cropped according to the requirement

image processing

I need to crop a recangle(tray) in an image even if its orientation is changed, i tried thresholding and regionprops for detecting the rectangle, but i need to crop it. I am new to this field, any help on how i can proceed.

thanks in advance. my image is very much similar to the image in the link below. http://medcaretips.com/images/tray-for-keeping-sample-tubes

Best Answer

Threshold, then you can get the bounding box in a number of ways, for example getting horizontal and vertical profiles by summing in each direction and then using find() to find the rows and columns where the intensity drops below some value. Or you can just pass the threshold image into regionprops and ask it for the bounding box. Then use imcrop. See my image segmentation tutorial BlobsDemo for an example, and come back if you're still having trouble.

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MATLAB: How to crop bigger size of blob in binary image and count its pixel .

Not sure what you mean. You can use imcrop() if you want. You can also find the bounding boxes if you want:

props = regionprops(binaryImage, 'BoundingBox');

To crop out each one individually, do this

for k = 1 : length(props)
    thisBB = props(k).BoundingBox;
    subImage = imcrop(binaryImage, thisBB);
    figure;
    imshow(subImage);
end

This is done in my Image Processing Tutorial

MATLAB: “uncollage” a collage image

See my Image Segmentation Tutorial: http://www.mathworks.com/matlabcentral/fileexchange/25157-image-segmentation-tutorial-blobsdemo. It will show you how you can threshold objects on a dark background and crop out their bounding box to separate images. Almost exactly what you want to do, except that you have color images. Basically you want to extract the color channels:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);

Then create a binary image:

binaryImage = redChannel == 0 & greenChannel  == 0 & blueChannel  == 0;

Then label pass it into regionprops

blobMeasurements = regionprops(binaryImage, 'BoundingBox');

Then use a loop that for each region, use imcrop() to extract the bounding box from the original rgb image and use imwrite() to save it to a disk file. Here's the relevant code from my tutorial, which I'm sure a smart guy like you can modify - just take out the stuff about what coin type it is, and add a call to imwrite().

message = sprintf('Would you like to crop out each coin to individual images?');
reply = questdlg(message, 'Extract Individual Images?', 'Yes', 'No', 'Yes');
% Note: reply will = '' for Upper right X, 'Yes' for Yes, and 'No' for No.
if strcmpi(reply, 'Yes')
  figure;
  % Maximize the figure window.
  set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
  for k = 1 : numberOfBlobs           % Loop through all blobs.
    % Find the bounding box of each blob.
    thisBlobsBoundingBox = blobMeasurements(k).BoundingBox;  % Get list of pixels in current blob.
    % Extract out this coin into it's own image.
    subImage = imcrop(originalImage, thisBlobsBoundingBox);
    % Determine if it's a dime (small) or a nickel (large coin).
    if blobMeasurements(k).Area > 2200
      coinType = 'nickel';
    else
      coinType = 'dime';
    end
    % Display the image with informative caption.
    subplot(3, 4, k);
    imshow(subImage);
    caption = sprintf('Coin #%d is a %s.\nDiameter = %.1f pixels\nArea = %d pixels', ...
      k, coinType, blobECD(k), blobMeasurements(k).Area);
    title(caption, 'FontSize', 14);
  end

Best Answer

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MATLAB: How to crop bigger size of blob in binary image and count its pixel .

MATLAB: “uncollage” a collage image

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