Quilt Pro will do what you want plus a lot more.
http://www.quiltpro.com It is also available for Mac and can be downloaded. There is a demo program you can try out. I use it for scanning in my fabrics and playing with the color options and figuring yardage. When I get a quilt idea, I scan in whichever fabrics I plan on using to test out the pattern and to make sure I have enough.