Need help with drawing sound

Hey Im in the middle of developing a patch for a semester project..

the basic idea is to --> track a fingerblob and its X and Y values on a glass plate with a webcam--> the movement of the finger will be stored in the lcd object

I have to loop the movement of the fingerblobs!!

I dont know if it is possible.. but I would like to create a 'scanning' line that travel across the lcd screen. When the scanning line sweeps across the lcd screen, the lcd object should activate the black pixels and not activate the white pixels. When activated I would like them to simply just send out a bang....

People should be able to keep on drawing with their fingers on the glassplate (adding more and more lines) while this scanning line travels across the glassplate... put otherwise, I would like to create a timeline which starts from the left and travels across the lcd object and keeps on looping!!!!!

So far I would like all the cordinates XY to send out a midi message, when activated in the lcd object...

maybe the lcd object is not the right solution, im aware of the jit.lcd obejct as well..

I hope you understand and interested in helping me!!

mvh Bjørn