square image size whitout changing in original image shape

Hi guys . i have an image (size is 256x158) for computing zernike momentum i have to change my image size to N x N for example 256 x 256 . but unfortunately my image shape will be changed . i want to have my original image without changing . could you help me how can i resize my columns and rows without changing in my original image shape ? i have an idea . how can i add white pixels to my image for resizing like that image i attached (center oval for example is my image and white background for resizing in N x N size )

Answer 1

[Joseph Cheng]

If you're looking to pad the columns as there are enough rows to get youre 256x256 then.

 Oimage = imread(____);  %your original image
 %ones padded to either side of image, multiply by the white color index.
 PadImage = [ones(256,49) Oimage ones(256,49)];

That should get you the 256x256 sized image. If you're trying to resize it so there is a 1.6 times magnification to scale the smaller columns to 256 and trim off the extra rows then imresize() should work out.

[hamed]

thanks a lot . it was work but i have 2 new problem 1 - when i double my image my original image convert to another image 2- when i add pad i have a vertical black line in my image

>>

[Joseph Cheng]

ah... okay well that would mean there is some variation on that edge that is not the "black" values. what you could do instead of padd it with the "ones" fill it with the values of the first and last column. or the average of the background (non-brain image).

i do not understand the "when i double my image my original image convert to another image" can you explain in another way?

[hamed]

with im2double solved my problem . my mistake was I = double(image);

[Image Analyst]

Another mistake is using a jpeg image for image analysis. Just look at those horrible compression artifacts.

I don't know what you did with im2double() and double() but it's not necessarily a mistake to use double() - I do it all the time and never use im2double().