If Light Image Resizer downloaded from ObviousIdea's website is flagged as a virus or considered unsafe by your anti-virus software, this is most likely a false positive.

It's a different case if you download it somewhere else, so to be sure you should only use the official download.

Our installer is flagged as WS.Reputation.1? [Click here for more information]

If you want to be sure, you can submit the file to online virus scanners, where it will be checked by a number of different anti-virus products:

In any case please contact us, and mention which antivirus product you are using. In addition you can submit the file to your anti-virus vendor, so they will analyse and whitelist it if needed.