How to enable gzip for images in iis7?

I set dynamic compression and static compression on in iis7 manager. So html,css,js content is compressed ok and i see in headers Content-Encoding:gzip, but not with image formats: jpeg, gif and even bmp.

Can you gzip an image?

Don't use gzip for image or other binary files Image file formats supported by the web, as well as videos, PDFs and other binary formats, are already compressed; using gzip on them won't provide any additional benefit, and can actually make them larger. To compress images, see Optimize images.

How do I enable gzip in IIS?

GZip Compression can be enabled directly through IIS. So we go to the “Turn Windows features on or off” and select “Dynamic Content Compression” and click the OK button.

Generally speaking, you wouldn't want to. JPEG, GIF, and most (internet) image formats are already compressed. Compressing them a second time would add a lot of server overhead for very little size gain (and possibly a loss).