Creating callouts or speech bubbles in GIMP

First open the basic image to which you would like to add the callouts to. This was my base image:



Add a new layer to the image by selecting Layer -> New Layer:



Give the new layer a new name (optional)


The new layer can now be found in the layers window:



Now select the Ellipse Select Tool from the Toolbox window



Draw an ellipse on the image where the callout is required:



In my case, I wanted the border line of the call out to have the same color as the cat's face. So I had to set my foreground colour to the cat's face color. To do so, select the Color picker tool in the toolbox. In the layer's window, select the Background layer.



With the Color picker tool click on the cat's face to set that color as the foreground color.



Select the new layer that was created in the first few steps:


Now select the fill tool and make sure "FG color fill" is selected.


Now click inside the ellipse. The image looks like this now:



Now click select -> Shrink.



In the next dialog, enter the size of the callout's border. In my case I wanted a 3 pixel border.



The selection now reduces by the number of pixels entered in the previous step:



Now click edit -> clear.


Now the border of the call out is nicely formed.



Now get rid of the selection (Select -> None)



Now to extend the call out, use the Path tool. Select click on points indicated:



After clicking on the 3rd point, hold the control key, hover over the 1st point and when the mouse pointer changes a little bit, click. This will make the selection a closed one.

Now draw lines over the selection by selecting Stroke selection:



In my case the size of the call out line is 3 pixels (entered previously in the shrink selection step). The same size is entered here too:



Now the image looks like this:



Using the same steps, make another call out for the mouse:



Now the lines within the call out arrows have to be removed. To do so, zoom in:



Select the Paths tool and go about clicking on the line segment that needs to be erased. Now select "Stock path" and select "Stock path from paint tool" and select "Erase" in the drop down (before doing this select the eraser tool in the tool bar and make sure the brush size [in the eraser tool properties] is correct) and stroke. This will erase the un-necessary parts and look like this:



Use, the Text tool and enter the desired text into the call out. Have Fun/ :-)

This tutorial is based on this article with more details and certain improvements.