How to capture image from the recorded project with *.camrec format

Move the time-slider to the frame you want to export,

Click "File" > "Produce special" > "Export frame as..." or press CTRL + F

Choose the name and location on where you want to save the file and click "Save".

@Mrtn answer is correct for Camtasia Studio 8. In CS 9, you still scroll the playhead to the exact frame you desire. Then go to "Share" > Export Frame As... or press CTRL + F

The exported file will be PNG format, which you can then preview or edit in any photo editor program like SnagIt.