I am using <https://www.codecogs.com/latex/eqneditor.php> 

And added my latex as follows:

```
 \begin{equation}
 SSIM(x,y)=\frac{{\left ( 2 \mu_x\mu_y+ C_1 \right )+ \left (2 \sigma _x_y+C_2\right)}} 
{\left(\mu_x^2+\mu_y^2+C_1)(\sigma_x^2+\sigma_y^2+C_2\right)}
  \label{eq:SSMI}
\end{equation}

```

I expected the following formula but instead of I got the error:!Double subscript. ...y+C\_1\right)+ ... 

[![enter image description here](https://i.stack.imgur.com/I9d4I.gif)](https://i.stack.imgur.com/I9d4I.gif)