中文摘要：

分析了现有的屏幕截取方法在多媒体网络教学中所存在的不足，提出了一种基于差值的动态屏幕截取快速算法，并给出了该算法的具体实现。该算法通过对屏幕信息变化的区域进行分析，将屏幕划分为小块矩形区域，动态提取并进行判断。采用广度优先搜索算法、权重策略、循环遍历机制与随机点策略，能够快速、有效地获取前后两屏信息的差值部分。实验证明，当前后两屏幕闾信息变化在一定范围之内时。该算法明显地提高了截屏速度，减少了对屏幕冗余信息的读取，提高了教学过程中屏幕信息交互的流畅性。

英文摘要：

Analyzed the shortage of the existing methods of screen capture which used in the multimedia network- based teaching system, a fast algorithm of screen capture based on image differentia was put forward, and then provided the implementation of the algorithm in detail. The algorithm analyses the changed region on the screen. The screen is divided into several rectangle parts which is selected and compared dynamically. Broad first search algorithm, weight strategy, searching loop tactic and random strategy is used to gain different parts of two screens rapidly and effectively. The experiments result shows that in a certain rang of the changes of the information between the two screens, the algorithm improves the speed of screen capture ,and decreases the reading of screen redundancy, improves smoothhess of delivering the screen information to each other.