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how to resize an object in binary image ?

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ElizabethR
ElizabethR on 20 Mar 2016
Commented: ElizabethR on 21 Mar 2016
i try to resize (minimize) an object in binary image, but I get the whole picture is to be small. even though I just wanted to minimize only its object. please help me. thanks

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Accepted Answer

Image Analyst
Image Analyst on 20 Mar 2016
If you want to shrink a binary image in place, without cropping out, then you can use imerode() to eat away outer layers of the binary blob(s).

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Image Analyst
Image Analyst on 20 Mar 2016
You can use padarray() to add black all around the image. This will enlarge the array. Then, to make it smaller, to any size, even the original size, you can use imresize():
binaryImage = padarray(binaryImage, 100);
binaryImage = imresize(binaryImage, [300, 300]); % Whatever size you want.
If you want it the same size as the original, do this:
[rows, columns] = size(binaryImage); % Save original size.
binaryImage = padarray(binaryImage, 100);
binaryImage = imresize(binaryImage, [rows, columns]); % Same size as original.
ElizabethR
ElizabethR on 20 Mar 2016
thank you very much Image Analyst, it working perfectly.. :D may i ask one question again ? i want to convert image into polar coordinate(unit circle) with the object is on the center of the circle. i try to convert this image using cart2pol, but i can get image like this. So, how to make this image ? :D thank you so much
Image Analyst
Image Analyst on 20 Mar 2016
You can create a circle mask as shown in the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F
So if the mask is true in the circle and false outside, do
binaryImage(~mask) = true;
For what it's worth, I've also attached a circle masking demo.

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More Answers (1)

Walter Roberson
Walter Roberson on 20 Mar 2016
You need to extract the object first and imresize() on the extracted part. Consider using regionprops with the Image property to get the extracted object.

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ElizabethR
ElizabethR on 20 Mar 2016
hi Wlater, thanks for answare my question. but, How to extracted the object ?
Walter Roberson
Walter Roberson on 20 Mar 2016
props = regionprops(YourBinaryImage, 'Image');
extracted_image = props.Image;
smaller_extracted = imresize(extracted_image, [64 64]); %example output size
ElizabethR
ElizabethR on 21 Mar 2016
hi Walter, thanks you so much.. it's working perfectly, now i can extract the object .. but, i want the background ( black ) still there.

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