Why does dilate and erode images produce black images?

4 views (last 30 days)
Did i do something wrong with nhood variable?
%% 1. Dilation and Erosion
%a. Apply dilation and erosion to “lung.jpg” using 3x3 structuring element (all pixel value is 1).
%Before applying dilation and erosion you must perform the thersholding to make the input image into binary one (threshold = 128).
lung = imread('lung.jpg');
bilung = imbinarize(lung,128);
nhood = strel(ones(3,3));
dilatedlung = imdilate(bilung,nhood);
erodedlung = imerode(bilung,nhood);
%b. Display original image, dilation image and erosion image within the same figure.
figure
subplot(1,3,1);
imshow(lung);
title('original img');
subplot(1,3,2);
imshow(mat2gray(dilatedlung));
title('dilated img');
subplot(1,3,3);
imshow(mat2gray(erodedlung));
title('eroded img');
%c. Get morphological gradient of “lung.jpg” and display it.
basic_gradient = dilatedlung - erodedlung;
figure
imshow(basic_gradient);
title('gradient');

Answers (2)

Image Analyst
Image Analyst on 18 Nov 2021
Try
basic_gradient = imabsdiff(dilatedlung, erodedlung);

Image Analyst
Image Analyst on 18 Nov 2021
You didn't use imbinarize correctly. Get rid of the 128.
%b. Display original image, dilation image and erosion image within the same figure.
figure
subplot(1,3,1);
imshow(lung);
title('original img');
subplot(1,3,2);
imshow(mat2gray(dilatedlung));
title('dilated img');
subplot(1,3,3);
imshow(mat2gray(erodedlung));
title('eroded img');
%c. Get morphological gradient of “lung.jpg” and display it.
basic_gradient = imabsdiff(dilatedlung , erodedlung);
figure
imshow(basic_gradient);
title('gradient');

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