Finding the compression ratio

I am using the code for SPIHT image compression shown in the link https://in.mathworks.com/matlabcentral/fileexchange/4808-spiht

How to find the compression ratio.

Answer 1

[Walter Roberson]

Log2 of the number of states that the input can be in, compared to log2 of the number of output states.

This is not the same as file size because files can have overhead.

[Renjith V Ravi]

Please clarify