GEM Raster

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|formattype=electronic
 
|formattype=electronic
 
|subcat=Graphics
 
|subcat=Graphics
|extensions={{ext|img}}
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|extensions={{ext|img}}, {{ext|ximg}}, {{ext|timg}}
 
|pronom={{PRONOM|x-fmt/159}}
 
|pronom={{PRONOM|x-fmt/159}}
 
|released=1985
 
|released=1985
 
}}
 
}}
'''GEM Raster''' (or '''GEM VDI Bit Image''', '''GEM Bit Image''', '''GEM Image''', '''GEM Bitmap''') is an image file format originally associated with the GEM operating environment by Digital Research. It was used by ''GEM Paint'' and ''Ventura Publisher'', and apparently was widely supported by Atari ST software.
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'''GEM Raster''' (or '''GEM VDI Bit Image''', '''GEM Bit Image''', '''GEM Image''', '''GEM Bitmap''', '''IMG''') is an image file format originally associated with the GEM operating environment by Digital Research. It was used by ''GEM Paint'' and ''Ventura Publisher'', and by a variety of Atari ST software.
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The format of bi-level images is well standardized, but the specification is ambiguous as to the format of color images. As a result, there are several incompatible flavors of color GEM raster images, some of which have their own names, such as '''XIMG''' (Extended GEM Bit Image), '''TIMG''' (TrueColor IMG), '''STTT''', and '''Hyperpaint'''.
  
 
== Identification ==
 
== Identification ==
Files begin with hex bytes <code>00 01 00 08</code> or <code>00 01 00 09</code>.
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Files begin with two bytes indicating the (big-endian) file version number. The version number is usually 1 (<code>0x00 0x01</code>), but some XIMG files have a version number of 2, and version number 3 has also been used.
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The next two bytes indicate the size of the header, in 2-byte ''words''. For example, a value of 8 means the header is 16 bytes, measured from the beginning of the file.
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The header size is at least 8 words, but extended versions of the format have a larger header.
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XIMG files have the ASCII signature "{{magic|XIMG}}" at byte offset 16.
  
 
== Specifications ==
 
== Specifications ==
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* [http://bitsavers.informatik.uni-stuttgart.de/pdf/digitalResearch/gem/Programmers_Toolkit/5149-2374-001_GEM3_Programmers_Toolkit_Version_3.1_Supplement_1989.pdf GEM/3 Programmer's Toolkit, Release 3.1 Supplement], sec. 9 p. 22
 
* [http://bitsavers.informatik.uni-stuttgart.de/pdf/digitalResearch/gem/Programmers_Toolkit/5149-2374-001_GEM3_Programmers_Toolkit_Version_3.1_Supplement_1989.pdf GEM/3 Programmer's Toolkit, Release 3.1 Supplement], sec. 9 p. 22
 
* [http://www.seasip.info/Gem/ff_img.html Format of GEM bitmap]
 
* [http://www.seasip.info/Gem/ff_img.html Format of GEM bitmap]
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* {{AtariForumWiki|IMG_file|Understanding color IMGs}}
  
 
== Software ==
 
== Software ==
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* [[Konvertor]]
 
* [[Netpbm]]: pbmtogem, gemtopnm
 
* [[Netpbm]]: pbmtogem, gemtopnm
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* [[XnView]]
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* {{Deark}}
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* [[RECOIL]]
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* [http://snisurset.net/code/abydos/ abydos]
  
 
== Sample files ==
 
== Sample files ==
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* http://cd.textfiles.com/clipart1996/TYPE/OTHER/
 
* http://cd.textfiles.com/clipart1996/TYPE/OTHER/
 
* http://cd.textfiles.com/fantaziasampler/CLIPART/IMG/
 
* http://cd.textfiles.com/fantaziasampler/CLIPART/IMG/
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* http://cd.textfiles.com/crawlycrypt2/crm_demo/images16/ (XIMG)
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* http://sylvana.net/1stguide/snaps/ (Version 3 files)
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* https://telparia.com/fileFormatSamples/image/gem/
  
 
== See also ==
 
== See also ==
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* [[GEM bitmap font]]
 
* [[GEM VDI Metafile]]
 
* [[GEM VDI Metafile]]
  
 
== Links ==
 
== Links ==
 
* {{EGFF|gemraster|GEM Raster File Format Summary}}, from the [[Encyclopedia of Graphics File Formats]]
 
* {{EGFF|gemraster|GEM Raster File Format Summary}}, from the [[Encyclopedia of Graphics File Formats]]
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[[Category:Atari graphics formats]]

Revision as of 20:39, 14 August 2020

File Format
Name GEM Raster
Ontology
Extension(s) .img, .ximg, .timg
PRONOM x-fmt/159
Released 1985

GEM Raster (or GEM VDI Bit Image, GEM Bit Image, GEM Image, GEM Bitmap, IMG) is an image file format originally associated with the GEM operating environment by Digital Research. It was used by GEM Paint and Ventura Publisher, and by a variety of Atari ST software.

The format of bi-level images is well standardized, but the specification is ambiguous as to the format of color images. As a result, there are several incompatible flavors of color GEM raster images, some of which have their own names, such as XIMG (Extended GEM Bit Image), TIMG (TrueColor IMG), STTT, and Hyperpaint.

Contents

Identification

Files begin with two bytes indicating the (big-endian) file version number. The version number is usually 1 (0x00 0x01), but some XIMG files have a version number of 2, and version number 3 has also been used.

The next two bytes indicate the size of the header, in 2-byte words. For example, a value of 8 means the header is 16 bytes, measured from the beginning of the file.

The header size is at least 8 words, but extended versions of the format have a larger header.

XIMG files have the ASCII signature "XIMG" at byte offset 16.

Specifications

Software

Sample files

See also

Links

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