How to get the inner and outer outlines of a boundary in an image?

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charuleelaa vanilavarasu
评论： Yushuo 2022-7-10
I'm trying to get the inner and outer outlines of the objects in an image to perform ioopl matching according to a paper i'm trying to implement. I want to contract my object boundary inwards and also expand it outward. eg:
how do i do this?

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Image Analyst
Image Analyst 2016-3-17
Assuming you have the initial green boundary, you can convert it into a binary image and then use imdilate or imerode to grow or shrink the boundary
mask = poly2mask(x, y, rows, columns);
bigMask = imdilate(mask, true(3));
bigBoundary = bwboundaries(bigMask);
smallMask = imerode(mask, true(3));
smallBoundary = bwboundaries(smallMask);
Change the 3 to some other, larger number if you want to grow or shrink by some different amount.
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charuleelaa vanilavarasu
charuleelaa vanilavarasu 2016-3-18
it doesn't seem to work. Im just getting a image with a blue boundary. i tried increasing the value 3. doesn't do the trick. If you could try it, that would be great thank you.

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Image Analyst
Image Analyst 2016-3-18
Try this:
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Read in color image.
rgbImage = imread('2.jpg');
% Display the image.
subplot(2, 2, 1);
imshow(rgbImage);
title('RGB Image', 'FontSize', fontSize);
grayImage=rgb2gray(rgbImage);
thresholdLevel=graythresh(grayImage);
% Display the image.
subplot(2, 2, 2);
imshow(grayImage);
title('Gray Scale Image', 'FontSize', fontSize);
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;
hold on
binaryImage = im2bw(grayImage,thresholdLevel);
% Invert it and extract the largest blob.
binaryImage = bwareafilt(~binaryImage, 1);
% Fill Holes.
binaryImage = imfill(binaryImage, 'holes');
% Display the image.
subplot(2, 2, 3);
imshow(binaryImage);
title('Binary Image', 'FontSize', fontSize);
% Display the image.
subplot(2, 2, 4);
imshow(rgbImage);
title('RGB Image with 3 outlines', 'FontSize', fontSize);
axis on;
hold on;
[B,~,~,rgbImage] = bwboundaries(binaryImage);
boundaries = bwboundaries(binaryImage);
visboundaries(boundaries, 'Color', 'b');
bigMask = imdilate(binaryImage, true(13));
bigBoundary = bwboundaries(bigMask);
% Display the boundary over the image.
visboundaries(bigBoundary);
smallMask = imerode(binaryImage, true(7));
smallBoundary = bwboundaries(smallMask);
% Display the boundary over the image.
visboundaries(smallBoundary, 'Color', 'm');
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Image Analyst
Image Analyst 2016-3-18
You have an old version. Go to the Mathworks site and download the latest version.
Ely Raz
Ely Raz 2017-12-30
How can I crop the jet in the RGB image subplot based on the jet binary image subplot dimensions?

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