Image Corp tool

I need a corp tool for our community. The members should be able to upload an image of them self and then be able to corp the image so they only get the part that they want. The aspect of these images will always be 90x120pixels. This is because all small thumbnails will be in 90x120 and to avoid an image to look stretched this is our aspect ratio of all images. So each time the width of the marquee tools width increase with 3 pixels the height is increased by 4. I need a javascript with this selecter/marquee tool that follow the aspect ratio. This javascript must be placed inside a form and send data to my phpscript on submit with cutting information from x,y (upper left corner) to x,y (lower right corner). I have included a file that shows the 2 functions that this tool shall handle.