# How do i Crop out the Only sclera portion from image of an eye ?

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Dipesh Gupta on 1 May 2016
Commented: Image Analyst on 28 Aug 2018
i have used Hough Transform to detect the radius of the Limb & its Centre. after that i used Chen-vese Active Contour to detect the Limb Portion & i got the its mask. but i need Help in subtraction of image so that i can get Only Sclera portion from the Original image of eye.
So help me Get the Only Schlera portion so that the output image have the Sclera with veins ? Thanks.
##Original Image
##Limb Detection with its Position & Radius.
## Active Contour Detection of Limb to Crop the Schlera Out.
L=rgb2gray(I);
BW1 = edge(L,'Canny');
imshow(BW1);
h = circle_hough(BW1, radii, 'same', 'normalise');
peaks = circle_houghpeaks(h, radii, 'nhoodxy', 15, 'nhoodr', 21, 'npeaks', 1);
imshow(I);
hold on;
for peak = peaks
[x, y] = circlepoints(peak(3));
plot(x+peak(1), y+peak(2), 'g-');
end
hold off
figure;
imshow(I);
a=peak(1);
b=peak(2);
c=peak(3);
m = zeros(size(I,1),size(I,2));
m(20:120,20:120) = 1;
seg = chenvese(I,'small',1000,0.02,'chan'); % ability on gray image
%-- End
imshow(seg);
##### 2 CommentsShowHide 1 older comment
Image Analyst on 28 Aug 2018
It's "Chan-Vese" after the authors of an algorithm for active contours. It's implemented in the activecontour() function of the Image Processing Toolbox.

Image Analyst on 2 May 2016
If you want the iris only on that particular image, I'd use imopen() on the binary image to separate it from the rest of the clutter. Or try imfindcircles(). Then call bwareafilt(binaryImage, 1) to extract only the iris since it will be the largest blob.
For finding the sclera, you can check the literature: http://www.visionbib.com/bibliography/contentsmedical.html#Medical%20Applications,%20CAT,%20MRI,%20Ultrasound,%20Heart%20Models,%20Brain%20Models. My guess is that they first convert to HSV colorspace and look for regions with low saturation and high value - that would segment out white regions.
Use the Color Thresholder app on the Apps tab on the tool ribbon. Or see the HSV segmentation demo in my File Exchange: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862
mak carlos on 7 Feb 2017
can u help me i has try run the code by matlab but it show out error on this sentence h = circle_hough(BW1, radii, 'same', 'normalise');

Prince Jindal on 28 Jan 2017
hi Dipesh
Just take pixel by pixel product of original image and complemented binary mask you generated.
Image Analyst on 28 Jan 2017
This is how you'd do that:
% Mask the image using bsxfun() function
This will give the middle image of the three images he posted in a comment to my Answer, so he's already doing this. I'm not sure what or if he had any questions after that.

RIDZA on 13 Jul 2017
%This code can be used if you know the x,y and r %only functioning using .jpg image % [filename, pathname] = uigetfile({'*.jpg';'*.bmp';'*.tif'}); [filename, pathname] = uigetfile({'/*.*'}); S = imread([pathname filename]);
%I = imread('088_1_2.jpg'); imageSize = size(I); % center and radius of circle ([c_row, c_col, r]) [xx,yy] = ndgrid((1:imageSize(1))-ci(1),(1:imageSize(2))-ci(2)); mask = uint8((xx.^2 + yy.^2)<ci(3)^2); croppedImage = uint8(zeros(size(I))); croppedImage(:,:,1) = I(:,:,1).*mask; croppedImage(:,:,2) = I(:,:,2).*mask; croppedImage(:,:,3) = I(:,:,3).*mask; imshow(croppedImage);
Laisa Fernochio on 4 Nov 2017
Hello Dipesh Gupta Can you give me the source code, I only need a code that detect the iris please

Emilia Badescu on 15 Apr 2018
Hello!! How can detect a value in this white area of the iris to distinguish it from the image that does not show this white area around the iris
Emilia Badescu on 30 Apr 2018
thank you, I'm reading the transformed Hough, but I just find the circle of the iris