RGB data help

Hi

I working on image processing in cyclone II.

I have RGB data, each channel having 8bit sample value.

image size is 640x480, 30Hz.

The data is following in the following manner:

R G B, R G B, R G B...

I want to draw a small rectangle or cross on the display.

please suggest me, how it is possible?

Your suggestion will be appreciated.

Thank You.