This technique should work for you.
1. Add the Blocks Random IN replicator from the Library>Replicator.
2. Select the replicator and in the Inspector, uncheck Shuffle order.
3. Go to the Sequence replicator behavior already attached to the replicator and remove the scale and position channels.
4. Add an Opacity parameter to the behavior(parameter>add>opacity). Set it to zero.
5. Select the image you want to draw on and apply an image mask (command-shift-m).
6. Drag and drop the replicator onto the image mask.
The replicator should now draw the image on from the top left to the bottom right. You can now modify things to get the look you want:
-Change the behavior length to control the speed.
-Change the Behavior>Spread parameter to control the fade as it draws on.
-Change the Cell Scale to set the “pixel” size.
-Change the replicator size, columns and rows depending on the size of the video and the space between cells.
You can come push the buttons or you can let me do my job.