最佳的一组脏兮兮的矩形

问题描述

问题：

性能非常关键，因此存在这个问题。

我猜想，这个问题总是会出现，绝对是在视频编解码器和远程桌面压缩领域。就我而言，在图形图像操作过程中，涉及多个用户同时在共享区域中绘图的问题是一个反复出现的问题。

有人知道已发布的算法或已知的您在过去使用过的解决方案？

谢谢！

解决方案

屏幕视频/远程桌面编解码器通常会将屏幕分成多个图块，然后仅为已更改的图块传输位图。平铺图像通常是ZLIB压缩的。

有多种方法可以改进，例如

• 为每个图块分配一个自己的边界矩形，以覆盖该图块中已更改的像素（以避免只有几个像素发生更改时重新传输整个图块）。
  
• 用压缩器的前一个内容填充压缩器（如果您正在录制被拖动的窗口或在2D游戏中移动的精灵，这将极大地提高压缩效率。）

例如Adobe Flash在其Screen Video 2编解码器中使用了所有三种技术的组合。

如果您不想使用压缩，瓷砖和瓷砖的组合。包围盒是一个很好的折衷。例如。如果在对角处只有两个变化的像素，那么只会更新这两个像素，但是如果您有一个分散变化的区域（例如，在文本编辑器中键入），则这些更改会合并为几个较大的矩形，这可能比把它分成数百个小矩形。）

I'm looking for an algorithm here, independent of specific programming language.

The problem:

Performance is critical, hence this question.

This problem crops up all of the time, definitely in video codecs and remote desktop compression areas, I presume. In my case, it is a recurring problem during graphical image manipulations that involve multiple users simultaneously drawing in a shared area.

Does anyone know of published algorithms for this or know of a solution you have used in the past?

Thanks!

解决方案

Screen video/remote desktop codecs generally divide the screen into tiles and then transmit bitmaps for the changed tiles only. The tile images are typically then ZLIB-compressed.

There are various ways to improve on this, e.g.

• Give each tile its own bounding rectangle, covering the changed pixels in that tile (to avoid re-transmitting the whole tile if only a few pixels have changed.)
• Prime the compressor with the previous contents of the tile (this greatly improves compression efficiency if you are recording a window being dragged or sprites moving in a 2D game.)

For example Adobe Flash uses a combination of all three techniques in its "Screen Video 2" codec.

If you don't want to use compression, a combination of tiles & bounding boxes is a good compromise. E.g. if you have just two changed pixels at opposite corners only those two pixels will be updated, but if you have a region with scattered changes (e.g. typing in a text editor) the changes are combined into a few large rectangles which is probably more efficient than breaking it into hundreds of small rectangles.)

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