pass in a raw pixelBuffer to the open command

It would be nice to open raw pixel buffers. This opens the possibility to manipulate pixel data from other sources than image files.

One project where this could be handy, would be my kinect2 nodejs library. In this library, I'm getting raw pixel data from the kinect cameras. I am now using a hacky workaround to do image manipulation & compression using lwip in this example:

https://github.com/wouterverweirder/node-kinect2/blob/master/examples/color-feed-browser-lwip-hack/index.js