Professional art software can be expensive, usually costing several hundred dollars. Many beginning book illustrators who cannot afford these programs are taking advantage of free downloadable art programs online. No single free program will meet all of your needs, but downloading several of these programs can create a robust toolset.
GIMP is a powerful freeware bitmap art program. It duplicates many of the functions available in Photoshop, the art industry standard, and is available for Linux, Mac and PC. For those illustrators used to a Photoshop user interface, there is even a plug-in you can download to make GIMP's layout similar to Photoshop. There are downsides, however. GIMP is not compatible with all digital tablets. Also, it cannot save files under a CMYK format, the print industry standard.
Artweaver, an alternative to GIMP, features a more friendly user interface similar to Photoshop. Like Photoshop, it has support for layers, gradients and different types of brushes. It also offers CMYK support. But Artweaver is only available for Windows-based computers and is unavailable for Mac or Linux.
Peacock Color Picker
The Peacock Color Picker program allows you to adjust the colours of your digital artwork. This is particularly important if you use freeware programs to create your artwork, as most of them save files in a RGB format. Printed artwork must be in CMYK format, which has a more limited colour range. In particular, several bright hues are missing from CMYK. Because many children's illustrations feature bright colours, a printed version of an RGB file will probably come out poorly unless you adjust it with a program such as Peacock Color Picker.
Reohix: Peacock Color Picker reohix.com/peacockcolorpicker.htm
Inkscape is the freeware equivalent of Adobe's Illustrator. Most people use it for layout designs, but it also has a feature that allows you to turn a bitmap art image into a vector-based one. The program makes the lines of your artwork cleaner and smoother.
PrimoPDF is a freeware PDF converter. It allows you to convert images and documents into Adobe Acrobat documents that are often used in the publishing industry. PrimoPDF is limited, but easy to use with a simple user interface. PrimoPDF is only available for PCs.