If you have a video that you first want it masked by a white background, and uncover the video as lines are drawn into it, you can use a jit.lcd with a white background, draw into it with black lines, and add that to your video. All the pixels that are white (255 255 255) in your jit.lcd matrix will be white in the summed output, and all the pixels that are black (0 0 0) in the jit.lcd will not affect the video.
This example shows a simple way of putting text into video, with the lines of text stored in a coll object. After loading the video sending a read message to jit.qt.movie, you can load each line by clicking the button in the middle of the patch.
One way to superimpose 2D graphics over a video is to draw into a jit.lcd object and then use alpha masking to overlay the jit.lcd contents on top of the video image.
Simple linear motion in 2D animation is achieved by interpolating between two points and successively drawing an object at each intermediate point, as demonstrated in the example on Animating 2D graphics.
In working with video and animation in Jitter, it’s important to remember that the effect of continuous motion is achieved by successive discrete images, each somewhat different from the preceding one. You can create that effect in 2D animation by repositioning graphic objects for each frame, according to a particular trajectory, such that the objects seem to be moving.
The jit.lcd object understands a variety of command messages for drawing simple things such as lines, geometric shapes, text, and pictures any place in a matrix.
Onscreen drawing of lines, shapes, text, and stored images is done using drawing commands derived from Apple's QuickDraw/Quartz systems for creating 2D graphics. The lcd object understands many such commands, and can serve as a 2D drawing surface (and/or animation stage) within a Max patch. Note that almost everything that can be drawn in the lcd object can also be drawn into a Jitter matrix with the jit.lcd object.