How to slice big picture on small pieces (256x256) for PhotoScroller

I have a big picture (3000x3000)pixels. How can i slice it on 开发者_如何学Pythonsmall pieces (256x256)?

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If you simply want to do this at build time, rather than run time, try using the ImageMagick 'crop' option

convert -crop 256x256 myoriginal.png mytiles_%d.png