With the Gmail Screenshot by cloudHQ Chrome extension, so you can do any of the following on your screen capture:

☑︎ Write text
☑︎ Crop
☑︎ Use arrows
☑︎ Pixelate sensitive information
☑︎ Include rectangular boxes or lines
☑︎ Get a link of your marked-up image to send to anyone!

To find out more about Gmail Screenshot, click here.
To install Gmail Screenshot, click here.
Instructions on how to get started are here.

.