Not sure why you want to do this... but if you where resizing before uploading I just found out this http://www.plupload.com/ it does all the magic for you in any imaginable method.
Unfortunatelly HTML5 resize only is suported with Mozilla borwser, but you can redirect other browsers to flash and silverlight.
I just tried it and worked with my android!.
I was using http://swfupload.org/ in flash, it does the job very well, but the resize size is very small. (cannot remember the limit) and does not go back to html4 when flash is not available.