For Full Screen Wallpaper - How do you resize photo ON PHONE??

I have photos that I have taken with the phone that I want to set as wallpaper.  Setting them as wallpaper though only fills a portion of the screen leaving black bars at top and bottom.  I've read in here that the photo needs to be resized to 240x480 or 480x240 for the full screen effect to kick in.  Can this be done on the phone itself WITHOUT sending the photo to a computer to resize in a photo shop program??