set the outside pixel values into zero.

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khaleed james 2016-3-1

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回答： Image Analyst 2016-3-1

hi, im doing a iris recognition. After iris circle (iris region) detection, i need an automatic cropping or masking method to mask the regions other than iris. and i found one of the method is to set the outside pixel. how to set the outside pixel values into zero or any others method how to extract the iris region?

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Answer 1

Muhammad Usman Saleem 2016-3-1

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Try from them

http://www.mathworks.com/help/images/ref/imcrop.html

http://www.mathworks.com/matlabcentral/fileexchange/31064-crop-image-with-selected-area

http://stackoverflow.com/questions/5528240/crop-an-image-in-matlab

http://www.mathworks.com/matlabcentral/answers/182712-how-to-crop-image-selected-area

http://www.mathworks.com/matlabcentral/answers/39987-cut-an-area-in-the-image

http://www.mathworks.com/help/images/cropping-an-image.html

https://www.researchgate.net/post/Is_it_possible_to_automatically_crop_images_in_MATLAB_from_any_image

Assinging 0 to outside pixels is not a correct idea. Image size and data remains as usuall

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Answer 2

Image Analyst 2016-3-1

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在 MATLAB Online 中打开

It looks like you already have coordinates for a circle. So just pass those in to poly2mask to create a mask. Then use it as logical indexes to zero out that part.

% Create mask from circle coordinates.
[rows, columns, numColorChannels] = size(grayImage);
irisMask = poly2mask(x, y, rows, columns);
% Mask outside the circle to black, 0.
grayImage(~irisMask) = 0;

After that you want to "extract the region". Exactly what does that mean? Do you want the mean inside the iris? Do you want to create a new smaller image by cropping the iris portion? By the way, it's not necessary to blacken the image outside the iris to do either of those.