calculation of PSNR cetween two images

If I am calculating PSNR of a image then should I use

PSNR=psnrtest(Original_image,reconstructed_image)

OR

Original_doubled_image=double(Original_image);
PSNR=psnrtest(Original_doubled_image,reconstructed_image)

Answer 1

[Guillaume]

As far as I know there's no psnrtest function in matlab or its toolboxes. The image processing toolbox has a psnr function however.

For psnr, both images must be of the same type and class. So if the reconstructed_image is double, then the original image should be double as well.Make sure that the intensity range of both images matches as well. double images usually have a range between 0 and 1.