ThunderScan compression

From Just Solve the File Format Problem
Jump to: navigation, search
File Format
Name ThunderScan compression
Ontology

ThunderScan compression, or ThunderScan RLE, is a compressed image format for 4-bit grayscale images. It can be used in TIFF files, and is identified by TIFF compression code 32809.

Contents

Format

The compression scheme is pixel-oriented, and uses run-length encoding and delta encoding.

Each coded byte represents one of four things, as indicated by the two highest bits:

Byte value Interpretation
00xxxxxx A run of pixels whose colors are the same as that of the previous pixel
01xxxxxx Three pixels whose colors are very similar to that of the previous pixel
10xxxxxx Two pixels whose colors are very similar to that of the previous pixel
11xxxxxx A single pixel of arbitrary color

Software

Sample files

Editors' notes

Libtiff calls this format "the 4-bit compression algorithm used by the ThunderScan program", but we have not been able to confirm its origin. Nearly all the information about it comes from libtiff.

ThunderScan is a scanner device for Apple II computers.

Personal tools
Namespaces

Variants
Actions
Navigation
Toolbox