Run-Length Encoding

Run-Length Encoding (RLE) is a simple and effective lossless compression technique used to reduce the size of data files by encoding consecutive repeated values. Here’s how it works:

Principle

• Run-Length Encoding: Compresses sequences of repeated data values by storing the data value and the number of times it repeats.

Example

Given a data sequence:

wwwwaaadexxxxxx

In RLE, this sequence is encoded as:

w4a3d1e1x6

How It Works

• Input Sequence: wwwwaaadexxxxxx

  • w occurs 4 times consecutively.
  • a occurs 3 times consecutively.
  • d occurs 1 time.
  • e occurs 1 time.
  • x occurs 6 times consecutively.

• Encoded Output: w4a3d1e1x6

  • Each character is followed by the count of its occurrences.

Advantages

• Simple: Easy to implement and understand.
• Effective: Works well for data with long runs of repeated values, such as simple graphics or binary data with large homogeneous areas.

Limitations

• Inefficiency: Less effective for data with few or no consecutive repeated values.
• Overhead: The encoding may increase the file size for data that does not have long runs of repeated values.

Run-Length Encoding is particularly useful in scenarios where data consists of long sequences of repeated values, such as in simple image formats or certain types of data logs.