I have used Photoshop for image editing. Is there an equivalent application under Linux?
Yes, there is. One such popular application program is GIMP (GNU Image Manipulation Program). Both programs (Photoshop and GIMP) share concepts relating to graphic design. Although, you may need more time to get the hang of GIMP as it has a different user interface.
If you are sort of a pro-level Photoshop user, you may notice that GIMP does not work at par. But GIMP is as functional as Photoshop. Aside from that, GIMP is free of charge, uses less computer memory, and can be used even under Mac or Windows. Imagine that you have worked on an image using GIMP under Linux desktop in your office. You have saved a copy in your USB disk or sent it to yourself via email. One day, you'd have to edit the file but, for some reasons, you must use a Macbook. Since GIMP is open source, you may freely download and install a Mac version of it. (The better if you carry the latest installer right in your USB drive). Isn't it a day-saver!