ThunderScan compression
From Just Solve the File Format Problem
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'''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. | '''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. | ||
== Format == | == Format == | ||
| − | The compression scheme is pixel-oriented, and uses [[run-length encoding]] and | + | 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: | Each coded byte represents one of four things, as indicated by the two highest bits: | ||
| Line 25: | Line 24: | ||
== Software == | == Software == | ||
| − | * | + | * {{Libtiff}} (read-only) |
== Sample files == | == Sample files == | ||
| − | * [ | + | * [http://download.osgeo.org/libtiff/pics-3.8.0.tar.gz pics-3.8.0.tar.gz] → libtiffpic/text.tif |
== Editors' notes == | == 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. | 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'' | + | Possibly-related things named ''ThunderScan'' include: |
| − | * [http://apple2online.com/web_documents/thunderscan_users_guide.pdf ThunderScan User's Guide] | + | * 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] | + | * 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: | + | [[Category:Graphics]] |
| + | [[Category:TIFF]] | ||
Latest revision as of 19:31, 14 December 2019
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
- LibTIFF (read-only)
[edit] Sample files
- pics-3.8.0.tar.gz → libtiffpic/text.tif
[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:
- An image file format supported by old versions of Photoshop (including v1.0.1 - see the source code)
- A scanner device for Apple II computers
