different between tiff and jpeg format in calculating MSE and PSNR

I got a code to calculate CR,bpp, MSE and PSNR. I works well for *.jpeg image but not for *.tiff. A message

"Error using  - 
Integers can only be combined with integers of the same class, or scalar doubles.

Error in sphit (line 38)
D = abs(X-Xc).^2;"

I cannot figure why it happen. The full code is:

X= imread ('lena.tif');   
[cr,bpp] = wcompress('c',X,'mask.wtc','spiht','maxloop',12)
Xc = wcompress('u','mask.wtc');
delete('mask.wtc')
colormap(pink(255))
subplot(1,2,1); image(X);  title('Original image')
axis square
subplot(1,2,2); image(Xc); title('Compressed image')
axis square

% Finally the MSE and the PSNR are computed.

D = abs(X-Xc).^2;
mse  = sum(D(:))/numel(X)
psnr = 10*log10(255*255/mse)

Answer 1

[Image Analyst]

When you see that error, it's fixed by converting the integer variable in the equation to a double.

D = abs(double(X) - Xc) .^ 2;

[Nik]

Thank you Image Analyst.. It WORKS!! :)

[Image Analyst]

Please read Cris's blog on PSNR: http://www.cb.uu.se/~cris/blog/index.php/archives/490#more-490