How to get INTENSITY along a spcific curve?
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Hi.
How can I get the intensity along a specific curve?
I mean for the following image, I want the intensity along the red circle. How to do so?
The original image is only the grayscale one and I have drawn the red one myself, so I know its data.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/155065/image.jpeg)
Shall I do so for the grayscale image or the binary one?
Thanks so much
Steven
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Accepted Answer
Ashish Uthama
on 14 Jan 2014
You could try using improfile, it will let you draw the cirle and then return the values along the profile.
Air code:
imshow(yourRawGrayImage)
% number of points you want to sample the profile with
N = 100;
profileValues = improfile(N)
10 Comments
Image Analyst
on 1 Apr 2021
Correct, I don't. It's just the intensity around the ellipse. Why do you think the spatial frequencies of that are meaningful? Maybe they're just more or less constant, perhaps with a little noise - basically the surrounding gray level of the blob. What information do you want?
Please start your own question with your own image and code attached.
More Answers (1)
Image Analyst
on 14 Jan 2014
Try this code:
clc; % Clear the command window.
clear; % Erase all existing variables. Or clearvars if you want.
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 24;
% Read in image
grayImage = imread('tire.tif');
% manually create a circle
subplot(2,2,1);
imshow(grayImage);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Let user create ellipse.
h = imellipse();
% Create a mask out of it
mask = createMask(h);
subplot(2,2,2);
imshow(mask);
title('Mask Image', 'FontSize', fontSize);
% Find boudnaries and plot over original grayscale image.
boundaries = bwboundaries(mask);
numberOfBoundaries = size(boundaries, 1);
subplot(2,2,1);
hold on;
thisBoundary = boundaries{1};
x = thisBoundary(:,2);
y = thisBoundary(:,1);
plot(x, y, 'g', 'LineWidth', 2);
hold off;
% extract all pixels along this profile
for k = 1 : length(x)
profile(k) = grayImage(y(k), x(k)); % logical indexing
end
subplot(2,2, 3);
plot(profile);
grid on;
title('Profile', 'FontSize', fontSize);
xlabel('Distance', 'FontSize', fontSize);
ylabel('Gray Level', 'FontSize', fontSize);
12 Comments
Image Analyst
on 30 Jun 2021
@Anna Schoonen, please post this in a thread of your own rather than using Steven's 7 year old question.
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