How to do screen capture in MacOSX in JPG instead of PNG

In MacOSX, we can easily do screen capture and save the image in PNG format to the desktop by the following keyboard shortcuts:

• Comand+Shift+3 : capture the whole screen.
• Comand+Shift+4 : capture a particular area by specifying the area using mouse, or by pressing spacebar to select a window.

Nevertheless, we may want to save the screen capture file in a different file format, such as JPG or maybe PDF. To do so, apply the following command in the terminal (the example is using JPG format):

$ default write com.apple.screencapture type jpg $ killall SystemUIServer

That's all :)