How do I create a 608 x 684 image to import into the load pattern image section?

Hello,

I am a new user.  I want to create a bit map file that is a sine wave and import it into the load pattern image section.  I tried generating a sin in excel and cropping it using Irfanview but it won't let me generate a 608 x 684 image.  Does any one have any suggestions about what I need to do to create a 690 x 684 bit map file that is a sine wave?

Thanks,

Elaine