How can I measure noise and sharpness of an image?
Simply, you can not 'calculate' the noise from single observation. Rather, you can estimate the target signal (denoised form), and then by using this estimation, you can determine the noise level. If the observation $y = x + n$ where the $x$ is target and $n$ is noise, after estimation of $x$ (via standart denoising methods), you can calculate the MSE, the SNR or other measures for noise level by using estimation $x$ and observation $y$. Of course these values will depend on the denoising method you use to estimate $x$, which can critically change the result.