Wikipedia
says: "data file or structure representing a generally
rectangular grid of
pixels, or points of color, on a
computer monitor,
paper, or other display device."
Windows/OSX Equivalents:
Adobe PhotoshopCorel Paint Shop Pro
Macromedia FireworksCorel Painter - try Krita or Gogh for Natural media painting or look below for
ArtRageNOTE:
Adobe Photoshop 7 and CS2 work under Wine or Crossover Office. As does Fireworks.
Also
ArtRage is reported to work well under Wine.
Look here.If you want completely open-source and free, but don't know which one to choose, then here is a comparison between Krita and The Gimp.