Grayed out Save button should offer better feedback

[StarManta]

I tried to copy an image out of a Google doc and save to a file, but I could not get the Save button to be not gray:

After I started writing this I tried to paste the image into Photoshop which also didn't work, so clearly the issue was with Google Docs not supporting copying pictures like that. That said, I think that if the Save button is grayed out, it should tell me why it's grayed out.

[pedjas]

I second this. It is confusing.

Also it would be great to have info what kind of content is in clipboard and maybe preview if possible?