Improved supershot sheet, right here.

Quality is improved and true colors show.
Turns out, it's not just 256 by 256 that works, but also 512 by 512, and any other of the similar matter.
I think it has something to do with 1024 bytes in a megabyte, and 512 and 256 being reagents that correspond to that.
Go ahead and try it out, I think you'll like what you'll see.
EDIT: This works with more than just shot data, but also sprites, and cutins, and all other of the similar matter. If you ever noticed that sometimes they look a bit fuzzy or blurry, try expanding the right and bottom canvas so it's either 256 by 256, 512 by 512, or 1024 by 1024. It'll come out clear as a crystal, I tried it myself. It goes in that pattern, if you're wondering whether it can go bigger if you need it.