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Thread Subject:
Extracting regions of interest from an image

Subject: Extracting regions of interest from an image

From: Bluebird

Date: 4 Aug, 2010 15:35:04

Message: 1 of 3

Hello all,

My problem is the follwoing, lets assume i have an image that has multiple people (i.e. two people standing), i want to manually extract the people. I want to do it manually like i am not looking for something fancy or automatic. I just want to view the image then move my mouse around the area, and the output is the selected regions.

Looking forward for your answer

Subject: Extracting regions of interest from an image

From: ImageAnalyst

Date: 4 Aug, 2010 15:42:36

Message: 2 of 3

On Aug 4, 11:35 am, "Bluebird " <wlo...@ryerson.ca> wrote:
> Hello all,
>
> My problem is the follwoing, lets assume i have an image that has multiple people (i.e. two people standing), i want to manually extract the people. I want to do it manually like i am not looking for something fancy or automatic. I just want to view the image then move my mouse around the area, and the output is the selected regions.
>
> Looking forward for your answer

---------------------------------------------------------------------------------------------------------------------------------
Maybe you could try, or adapt, my freehand masking demo:


% Change the current folder to the folder of this m-file.
% (The line of code below is from Brett Shoelson of The Mathworks.)
if(~isdeployed)
cd(fileparts(which(mfilename)));
end
clc; % Clear command window.
clear; % Delete all variables.
close all; % Close all figure windows except those created by imtool.
imtool close all; % Close all figure windows created by imtool.
workspace; % Make sure the workspace panel is showing.
fontSize = 20;

% Read in standard MATLAB gray scale demo image.
grayImage = imread('cameraman.tif');
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.
message = sprintf('Left click and hold to begin drawing.\nLift mouse
button to finish');
uiwait(msgbox(message));
hFH = imfreehand();

% Create a binary image ("mask") from the ROI object.
binaryImage = hFH.createMask();
% Display the freehand mask.
subplot(2, 2, 2);
imshow(binaryImage);
title('Binary mask of the region', 'FontSize', fontSize);

% Get coordinates of the boundary of the freehand drawn region.
structBoundaries = bwboundaries(binaryImage);
xy=structBoundaries{1}; % Get n by 2 array of x,y coordinates.
x = xy(:, 2); % Columns.
y = xy(:, 1); % Rows.
subplot(2, 2, 1); % Plot over original image.
hold on; % Don't blow away the image.
plot(x, y, 'LineWidth', 2);

% Burn line into image by setting it to 255 wherever the mask is true.
burnedImage = grayImage;
burnedImage(binaryImage) = 255;
% Display the image with the mask "burned in."
subplot(2, 2, 3);
imshow(burnedImage);
title('New image with mask burned into image', 'FontSize', fontSize);

% Mask the image and display it.
% Will keep only the part of the image that's inside the mask, zero
outside mask.
maskedImage = grayImage;
maskedImage(~binaryImage) = 0;
subplot(2, 2, 4);
imshow(maskedImage);
title('Masked Image', 'FontSize', fontSize);

% Calculate the mean
meanGL = mean(maskedImage(binaryImage));
message = sprintf('Mean value within drawn area = %.3f', meanGL);
msgbox(message);

Subject: Extracting regions of interest from an image

From: Bluebird

Date: 4 Aug, 2010 15:52:04

Message: 3 of 3

Thank you. It worked perfectly and does exactly what i am looking for.

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