ThunderScan compression

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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.
 
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.
+
Possibly-related things named ''ThunderScan'' include:
* [http://apple2online.com/web_documents/thunderscan_users_guide.pdf ThunderScan User's Guide]
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* An image file format supported by old versions of [[Photoshop]] (including v1.0.1 - see the [https://computerhistory.org/blog/adobe-photoshop-source-code/ source code])
* [http://apple2online.com/web_documents/thunderscan_iigs_software_guide.pdf ThunderScan GS Software Guide]
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* A scanner device for Apple II computers
 +
** [http://apple2online.com/web_documents/thunderscan_users_guide.pdf ThunderScan User's Guide]
 +
** [http://apple2online.com/web_documents/thunderscan_iigs_software_guide.pdf ThunderScan GS Software Guide]
  
 
[[Category:Graphics]]
 
[[Category:Graphics]]
 
[[Category:TIFF]]
 
[[Category:TIFF]]
[[Category:Apple II series]]
 

Latest revision as of 19:31, 14 December 2019

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

[edit] 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

[edit] Software

[edit] Sample files

[edit] 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.

Possibly-related things named ThunderScan include:

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