Negative value for PSNR after image enhancment in MATLAB
<p>I have done this so far. After image enhancement in frequency domain for assessment, I have calculated PSNR. The value of PSNR and SNR is negative.</p>

<p>Further, the class of input and output image is double. </p>

<pre><code>ref = imread('img.tif');
ref=im2double(ref);
%A = processing(ref);
%Calculate the PSNR.
[peaksnr, snr] = psnr(A, ref);
</code></pre>

<p>Can someone help me further?</p>