MATLAB: Polygon ROI extraction from an image

Image Processing Toolboxpolygon roi

Hi, I want to extract a polygon ROI from an image and work with that ROI further. How can I extract the ROI from the image and save it as an array??

Best Answer

Use functions like imfreehand(), roipoly(), roipolyold(), poly2mask(), rbbox(), imrect(), and/or imcrop().

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MATLAB: How to extract pixel data from a RGB / Grayscale image by specifying a region of interest

There are three different ways this can be achieved. The three examples are shown below:

%%Method 1: Sets image to be transparent except the ROI
I = imread('peppers.png');
image(I); axis off;
disp('please selct the Region Of Interest')
ROI = roipoly(I); % select a closed polygon

myImage = findall(gcf,'type','image');
set(myImage,'AlphaData',ROI);

Method 2

I= imread('peppers.png'); 
image(I); axis off;
disp('please selct the Region Of Interest')
ROI = double(roipoly); % select a closed polygon
ROI = uint8(ROI); % since original image was of type uint8
figure
I2 = zeros(size(I)); % create a new image 
I2(:,:,1) = ROI.*I(:,:,1);
I2(:,:,2) = ROI.*I(:,:,2);
I2(:,:,3) = ROI.*I(:,:,3);
image(uint8(I2)); axis off;
%%Method 3: Utilizes the IMCROP functionality
I= imread('peppers.png');
imshow(I);
rect = [290 160 220 165];
I2= imcrop(I,rect);
figure
imshow(I2);

MATLAB: I extract the ROI as separate image? in other words, i want to extract the polygon selection as separate image?? My Roi is in the link and highlighed and i want that ROI as separate image

You have to get the bounding box from your polygon using max() and min(). Then simply use imcrop() to get a cropped image, followed by imwrite() if you want to save it to disk.

Best Answer

Related Solutions

MATLAB: How to extract pixel data from a RGB / Grayscale image by specifying a region of interest

MATLAB: I extract the ROI as separate image? in other words, i want to extract the polygon selection as separate image?? My Roi is in the link and highlighed and i want that ROI as separate image

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