Hawkynt

Delta Filter

Pure, size-preserving delta transform: each byte is stored as the difference from the byte a fixed distance behind it (distance=1 here), with no entropy coding or run-length pass. Used as a predictor step ahead of a general-purpose compressor. Generalizes to any fixed distance (e.g. sample width or pixel stride); this instance fixes distance=1 to match CompressionWorkbench’s BB_Delta default.

Properties

Property	Value
Category	Compression Algorithms
Sub-category	Transform
Security status	Not classified
Complexity	Not specified
Inventor	Various (general technique)
Year	1950
Origin	❓ Unknown
Source	algorithms/compression/delta-filter.js

Security

Status: not classified — treat as unverified.

No vulnerabilities are recorded for this implementation.

Documentation

• Delta Encoding - Wikipedia
• PNG Delta Filters
• Time Series Compression

References

• PNG Reference Implementation
• TIFF Differencing Predictor
• CompressionWorkbench DeltaFilter (reference implementation)

Test vectors

4 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Empty data test

Source: Edge case test

Field	Value
input	(empty)
expected	(empty)

Vector 2 — Single byte test - first distance bytes are copied unchanged

Source: Minimal delta test

Field	Value
input	41
expected	41

Vector 3 — Incrementing sequence - pure delta, no compression

Field	Value
input	0a0c0e10
expected	0a020202

Vector 4 — Regression: 256 repeated bytes - output length equals input length (no RLE)

Source: Regression test distinguishing this from the Delta + RLE compressor

Field	Value
input	61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161 61616161616161616161616161616161
expected	61000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000

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