GIMP is not your typical program for drawing, but is is the only thing related to graphics that is installed on my linux. So I have this screenshot and I want to draw a red rectangle around the part that needs to be clicked. This is how:
- Open your graphic file with GIMP.
- Use the "Rectangle Select Tool" and mark the place where you want your rectangle to be.
- Select the color you want to draw the rectangle in as foreground color (in my case that would be red).
- In the menu "Edit" choose "Stroke selection".
- In the dialogue that comes up, choose "Stroke line" with "solid colour" (it will take the current foreground color), you can adjust the width and if you open up "Line style" you can do more things (e.g., rounded edges).
- Click "Stroke" and voila!