You can download GIMP at http://www.gimp.org/.

When GIMP opens, you will see three parts. As can be seen in the image above, the part on the top left is the pallet where you pick your manipulation tool such as painting or erasing. The part on the bottom right is where you pick what your tool will look like, for example if your paint brush will be thick or thin. And the middle part is where you do your work.

A good way to get oriented in GIMP is to watch a tutorial such as
http://www.youtube.com/watch?v=8LmW5ndnEqw.

Using a scanner, you can convert a picture that your child has drawn into a digital image (keep it as a “bmp” file). Then you can load that image into GIMP. The large image shown above is of a comic book cover my son drew. Zoom in and look at the pixels using the menu Tools → Zoom. You can draw a box around a small area to zoom in once you have done that. You should see little squares called pixels, as can be seen in the image to the right. We used to say that “pictures don’t lie,” but now we view pictures as being made up of pixels, which allows them to be anything. Pixels are the precise conversion point between the continuous, physical world and the discrete, digital one.

You and your child can then modify the image. The eraser tool on the left can be used to remove pixels. You can pick the paint brush tool to paint on the picture, and you can fill in areas of the picture using the bucket fill tool (as I have done on the large image shown above). After manipulating the picture, you can then print out the new image for your child to see the complete cycle from physical artifact to digital artifact and back to physical artifact.

Additionally, once you have played around with the tools, you can watch this great tutorial on how to manipulate images taken from a digital camera
http://www.youtube.com/watch?v=3RtFt6axp5s&feature=related.

Since movies are just sequences of images, understanding how camera images can be manipulated gives your child a sense of how special effects are done in movies. Another theme of The Curiosity Cycle is that we should give children as many such glimpses of the world as possible. These glimpses allow children to create model fragments that jumpstart curiosity by giving them a reason to reach out for new information.

GIMP is a powerful tool, and therefore it can be a little overwhelming at first. Fortunately, GIMP has a robust user community, and many questions can be answered by Google search and watching online tutorials. Learning how to learn to use tools such as GIMP is itself an important skill, and may be even more beneficial for your child than learning about GIMP itself.

Jonathan Mugan is a computer science researcher specializing in machine learning and AI. He completed a postdoc at Carnegie Mellon University and  received a PhD in Computer Science from the University of Texas at Austin. He recently completed a book: The Curiosity Cycle: Preparing Your Child for the Ongoing Technological Explosion. You can follow him @jmugan.