I don't know for sure which camera you have, so I can't get too detailed

Canon A1100 IS
Canon SD1100 IS

Most likely cause is that you have "Digital Zoom" enabled.
Digital Zoom should be turned off or disabled.
Digital Zoom degrades your picture.

In case you have something set unintentionally I suggest you also do a "Reset All"
Look at the Index in the back of the User Manual and look for "Reset All".
That resets the camera to factory settings.

You should check Digital Zoom again because "reset all" might turn-on the digital zoom.
Turn-off digital zoom.