MATLAB: How to do “the black top-hat transformation”

bottom hatfilteringimage analysisimage processingImage Processing Toolboxtop hat transformation

after filtering the image i want to perform a black top hat transformation but could not find any information about it. please, any one help me .

Best Answer

Perhaps you're talking about the "bottom hat filter".

IM2 = imbothat(IM,SE) performs morphological bottom-hat filtering on the grayscale or binary input image, IM, returning the filtered image, IM2. SE is a structuring element returned by the strel function. SE must be a single structuring element object, not an array containing multiple structuring element objects.

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MATLAB: Can i use imerode() function to perform top-hat transform

You can achieve the same result as returned imtophat function only using imerode and imdilate.

% Load the image

original = imread('rice.png');
% Define the morphological structuring element (you can change it according to your application)

se = strel('disk', 12);
% Perform top-hat filtering without using imtophat(__)
openedImg = imdilate(imerode(original, se), se);
tophatFiltered1 = original - openedImg;

Now, calculate the same using imtophat

% Load the image
original = imread('rice.png');
% Define the morphological structuring element (you can change it according to your application)
se = strel('disk', 12);
% Perform top-hat filtering using imtophat(__)
tophatFiltered2 = imtophat(original, se);

Check if both approaches are giving the same results

isequal(tophatFiltered1, tophatFiltered2)
ans =
  logical
   1

MATLAB: Detecting playing cards by separating each card in the image

Please show the original image.

If the background behind the cards is a different color than the cards, like black background and white cards, then you can simply threshold, call imfill, and label then use ismember to create a mask for each card.

backgroundMask = ....... % Do color segmentation.
allCardsMask = imfill(~backgroundMask, 'holes');
% Extract only the 3 largest blobs
allCardsMask = bwareafilt(allCardsMask, 3);
labeledImage = bwlabel(allCardsMask);
cardMask1 = ismember(allCardsMask, 1);
cardMask2 = ismember(allCardsMask, 2);
cardMask3 = ismember(allCardsMask, 3);

For color segmentation routines, see http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

Your edge detection method could have a lot of problems if your edges are not completely connected, like in the upper right corner of your card on the right.

To identify the cards, you might use SIFT but a simpler way might be to simply count the number of colored pixels on each card in each color channel. It could be that every card has a unique count for R, G, and B. Then you could simply look up that number in a lookup table that you've filled up in advance with the "official" counts for each card. This would probably be far simpler than SIFT or SURF.

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MATLAB: Can i use imerode() function to perform top-hat transform

MATLAB: Detecting playing cards by separating each card in the image

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