Definition:  Software that allows you to manipulate images: convert from one format to another, resize, crop, touch up, apply filters, and more.

Tools:

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• FastStone
• GIMP
• GoogleSketchUp: Easy-to-use 3D modeling software (free; Mac/PC)
• iPhoto
• irfanView [Review]: Easy-to-use image editor and viewer (free; PC)
• Photoshop
• Picassa
• UVic Image Markup Tool [Review]: Facilitates image markup: "describe and annotate images, and store the resulting data in TEI XML files"
• XnView