I want to interpolate extracted ROI. Please help me with coding.

 p= imread('knee.jpg');  
     figure;
   imshow(p);
   img = imcrop;
   k=imshow(img);
   imwrite(k,'knee2.jpg');
z=imread('knee2.jpg');
figure;
[x,y]=meshgrid(1:256,1:256);
a=2;
for i=1:256;
    for j=1:256;
x1(i,j)=a*x(i,j);
y1(i,j)=y(i,j)/a;
    end
end
% Do the interpolation 
z1=interp2(x,y,z,x1,y1,'bilinear');
imshow(z1);

[Image Analyst]

I don't even know what a "interpolate extracted ROI" is.

First, read this http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer then improve your post by attaching knee.jpg so people can actually run your code.

[mounika siripurapu]

I selected region of interest from an image.Now I want to perform linear interpolation to improve the quality of the image.

[John D'Errico]

Linear interpolation will not improve image quality. That only works in the TV shows, where you can blow up a single pixel into a readable picture of a license plate. Any problems that were in the original will still be there, with sometimes new artifacts introduced.

[mounika siripurapu]

Thank you. But what type of interpolation method can be used to improve the quality of an image by increasing number of pixels. Kindly provide me coding if possible.