GIMP is a freeware graphics and photo-editing application. GIMP almost entirely uses bitmap based images. However, as with many bitmap editors, the letter shapes produced by the text tool are more or less vector graphics, and exist on a separate text layer in the layers panel. You may want to combine this text with other design elements in such as way to "rasterise" it, turning it into an ordinary graphic layer.
Start the GIMP application. Select "File" from the menu at the top and choose "Open." In the dialogue that appears locate and open a file containing a text layer you want to rasterise.
Go to the "Layers" panel and right click on the text layer. From the options, choose "Discard Text Information." This does not, as you might think form the name, delete you text. Instead, it turns it into a standard graphic by rasterising it.
Select "File" from the menu and choose "Save."