Data Compression – AP CSP | ShowMeClass

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Data Compression

AP CSP · Unit 1: Digital Information

Learning Objectives

Understand lossless vs lossy compression

Apply Run-Length Encoding (RLE)

Calculate compression ratios

Recognize tradeoffs in compression

Key Concepts

Lossless: Original data perfectly recoverable (PNG, ZIP, FLAC)

Lossy: Some data permanently lost for smaller size (JPEG, MP3)

RLE: Run-Length Encoding — replaces runs of same character with count+char

Ratio: compressed size / original size

Colors

Original data

Compressed (savings)

Overhead / lost

CompressionRLELossless

Method:RLE

Ratio:-

Savings:-

Original Data

Characters: 0 Bits: 0

Compressed (RLE)

Characters: 0 Bits: 0

Compression Ratio

- - -

COMPRESSION EFFECTIVENESS BY REPETITION

Input Text

Example Inputs

Compression Type

Lossy Quality 100%

Analysis

Quick Quiz▼

1. RLE compresses "AAABBC" as:

A3B2C1 3A2B1C ABC321 AAA-BB-C

2. Which is a lossy compression format?

PNG ZIP JPEG FLAC

3. A compression ratio of 0.5 means:

File doubled in size File is now half its original size No compression occurred All data was lost