Is my .img file corrupted?
Usually when downloading files (very likely for software) you have a checksum provided by the supplier. The checksum is nothing else but the hash value of the file you're going to download. Quite often this is MD5, but due to the collision potential in MD5 it starts to drift towards SHA (SHA1 mostly, somtimes SHA2).

After your download has finished, you compute the hash on the file yourself and compare the value with the one presented by the download page (or other source). If the two values match, this means that your download equals the file supplied on the website.

I started my VM for accessing such sites and had a look if there is a MD5 hash present. Right next to the download link, it was and that's the value I have copied to my comment. Therefore, if you follow the procedure I have written down above and look for such a hash value (check for MD5 or MD5SUM, SHA1 or SHA1SUM) you don't need any third-party assistance.