MATLAB Answers

Mehwish
0

Image resize image in matlab

Asked by Mehwish
on 13 Jun 2013
Hi, I am facing a blurring issue in the below code:
I = imread('waterframe-1.png');
I=imresize(I,[16 16]);
I=rgb2ycbcr(I);
I=ycbcr2rgb(I);
I=imresize(I,[256 256]);
I=ycbcr2rgb(I);
imshow(I);
Any help in this will be very highly appreciated
Thanks Mehwish

  1 Comment

Jan
on 13 Jun 2013
You forgot to mention any dteilas about the problem. What exactly do you see and what do you expect?

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4 Answers

Answer by Benoît THOUY on 13 Jun 2013
 Accepted Answer

Hi,
When upsampling, you have to deal with interpolation in order to predict missing pixels. As you do not know all 256*256 pixels with only 16*16 pixels, it uses some kind of "averaging" closest pixels to compute all pixels.
imresize uses bilinear interpolation by default. You can change to bicubic interpolation to have more "sharp" edges, but it will be blurred anyway. Nearest-neighbor interpolation will give you a "block" effect so no blur but big [16 16] squares. It is up to your choice. See documentation of imresize: www.mathworks.com/help/images/ref/imresize.html

  1 Comment

Mehwish
on 14 Jun 2013
Thanks a lot. It clears up a lot of mess in my head.
Regards
Mehwish

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Answer by Chandra Shekhar on 13 Jun 2013
Edited by Chandra Shekhar on 13 Jun 2013

dont resize original image to [16 16] make it as it is.
follow following code to get more info
I = imread('waterframe-1.png');
I=imresize(I,[256 256]);
I=rgb2ycbcr(I);
I=ycbcr2rgb(I);
I=imresize(I,[256 256]);
I=ycbcr2rgb(I);
figure;imshow(I);

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Answer by Mehwish
on 13 Jun 2013

Yup. I know it works. Thanks for the quick response. This is a short version of the algorithm which I am implementing. And the whole algorithm revolves around resizing the image to 16X16 and the conversion to ycbcr. So not resizing is out of question.

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Answer by Mehwish
on 13 Jun 2013

@ Jan I see blurring of the image and I expect to resolve it with some filter maybe....

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