Is there a javascript png library that allows specifying the number of colors (256

Is there a javascript png library that allows specifying the number of
colors (256

References

Reference NO 1

http://en.wikipedia.org/wiki/Portable_Network_Graphics

Reference NO 2

http://stackoverflow.com/questions/10635308/output-300-png-images-with-correct-filenames-from-svg-or-svg-via-canvas

Reference NO 3

http://sixrevisions.com/web_design/web-designers-guide-to-png-image-format/

Reference NO 4

http://www.libpng.org/pub/png/pngfaq.html

Reference NO 5

http://www.oreillynet.com/pub/a/server-administration/excerpts/9780596522315/optimizing-images.html

Reference NO 6

https://developers.google.com/speed/pagespeed/module/filter-image-optimize?hl=de

Reference NO 7

http://www.smashingmagazine.com/2009/07/15/clever-png-optimization-techniques/

Reference NO 8

http://www.turnkeylinux.org/blog/png-vs-jpg