A subway LED advertisement simulation application

Backgroud:

 When you are travelling in a moving Beijing subway train, you probably will see many LED advertisements moving outside the the train as fast as you do. So you will feel they are relatively static to you. Those LED advertisements are not shown on a very long continuous screen, but on many separate very narrow LED bars. The images on each bar will change at a frequency corresponding to the train's speed detected by some sensors, and each time the bars will show just a portion of the whole advertisement image. Due to the persistence of vision, you will then see the whole image. The frequency of changing the different portions is the key to make the image static to you.

Objective:

 This application is trying to simulate the LED bars and the feeling of watching them inside a train. The user are supposed to be on the train, thus the screen is what you see from the train. There are two parameters can be adjusted: the speed of the train (equivalent to the speed of the LED bars), the frequency to change the images on the bars. By tuning these two parameters, you would see different effects: the advertisement is narrowed and moving faster than the train or the advertisement is broadened and moving more slowly than the train. Only when the train's speed and the changing frequency are coordinated, the ads would be static to you and at the normal ratio.

The above GIF shows the static effect of the LED bars. The source code could be downloaded at:
https://www.dropbox.com/s/iekqtofxqfygrgl/Advertisement.rar