实现运行长度编码 [英] Implementing run-length encoding

问题描述

我写了一个程序来执行运行长度编码。
在典型情况下，如果文本

I've written a program to perform run length encoding. In typical scenario if the text is

AAAAAABBCDEEEEGGHJ

运行长度编码将使其

A6B2C1D1E4G2H1J1

，但每个非重复字符都添加了额外的1。因为我压缩BMP文件与它，我去了一个想法，放置一个标记$来表示一个重复的字符的出现（假设图像文件有大量的重复文本）。

but it was adding extra 1 for each non repeating character. Since i'm compressing BMP files with it, i went with an idea of placing a marker "$" to signify the occurance of a repeating character, (assuming that image files have huge amount of repeating text).

所以它看起来像

$A6$B2CD$E4$G2HJ

对于当前示例，它的长度是相同的，但BMP文件有一个显着的差异。现在我的问题是解码。因此，一些BMP文件在原始文件中具有模式 $< char>< num> ie $ I9 文件，所以在压缩文件中我也会包含相同的文本。 $ I9 ，但是解码后会把它作为重复的我重复9次！所以它产生错误的输出。我想知道的是，我可以使用哪个符号来标记重复字符的开始（运行），使其不与原始源冲突。

For the current example it's length is the same, but there's a noticable difference for BMP files. Now my problem is in decoding. It so happens some BMP Files have the pattern $<char><num> i.e. $I9 in the original file, so in the compressed file also i'd contain the same text. $I9, however upon decoding it'd treat it as a repeating I which repeats 9 times! So it produces wrong output. What i want to know is which symbol can i use to mark the start of a repeating character (run) so that it doesn't conflict with the original source.

推荐答案

为什么不把原始文件中的 $ 编码为 $$ 在压缩文件中？

Why don't you encode each $ in the original file as $$ in the compressed file?

和/或使用一些其他字符代替 $

And/or use some other character instead of $ - one that is not used much in bmp files.

另请注意，BMP格式有RLE压缩内置 - 查看这里，靠近页面底部 - 在图像数据和压缩下。

Also note that the BMP format has RLE compression 'built-in' - look here, near the bottom of the page - under "Image Data and Compression".

我不知道你使用你的程序，或者它只是为了学习，但如果你使用官方bmp方法，你的压缩图像在查看之前不需要解压缩。

I don't know what you're using your program for, or if it's just for learning, but if you used the "official" bmp method, your compressed images wouldn't need decompression before viewing.

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