Base85 (Ascii85)
Base85 (Ascii85) encodes 4 bytes as 5 ASCII characters, an expansion of 5/4 — more compact than Base64's 4/3.
Purpose
It represents binary data in ASCII channels with lower overhead, and is commonly used in PDF and PostScript.
Mechanism
Each 4-byte group is packed into a 32-bit big integer and repeatedly divided by 85 to yield five 0-84 indices, each offset by 33 to map into ASCII 33-117. An all-zero group may be compressed to the single character z.
Use cases
- PDF object stream encoding
- PostScript data embedding
- Binary embedding in document formats