SummaryCocktail, from, is a useful utility for Apple Mac computers that allows you to tweak system settings not accessible through the System Preferences. An example of this is the default image format of screen capture images.

Screen Capture. Similar to the Snipping Tool in Windows, Apple computers have mechanism for capturing the entire screen or portions of the screen. To capture the entire screen, press and hold Shift+Command+3. To capture a portion of the screen, press and hold Shift+Command+4, and then define the area to be captured by clicking and dragging your mouse to draw a square or rectangle around the area you are capturing (starting at one of the top left/right or bottom left/right corners).

Best Image Quality. To ensure you have the best image quality for screen captures, you can use the Cocktail utility program and go to the Interface options. Next to Screenshot file format, choose PNG from the drop down list (as shown below). You can also set another location other than the Desktop as the default location.