GEM Raster

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|formattype=electronic
 
|formattype=electronic
 
|subcat=Graphics
 
|subcat=Graphics
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|extensions={{ext|img}}, {{ext|ximg}}
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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
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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.
 
'''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''', '''STTT''', and '''Hyperpaint'''.
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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 ==
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Files begin with bytes <code>0x00 0x01</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'' (i.e. a value of 8 means the header is 16 bytes, measured from the beginning of the file).
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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 (<code>0x00 0x08</code>), but extended versions of the format have a larger header.
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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 a header size of 59 words (<code>0x00 0x3B</code>). They have an ASCII signature of "<code>XIMG</code>" at offset 16.
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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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* [http://www.atari-forum.com/wiki/index.php?title=IMG_file Understanding color IMGs]
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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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* [[FFmpeg]]
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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/fantaziasampler/CLIPART/IMG/
 
* http://cd.textfiles.com/fantaziasampler/CLIPART/IMG/
 
* http://cd.textfiles.com/crawlycrypt2/crm_demo/images16/ (XIMG)
 
* 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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* {{DexvertSamples|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]]

Latest revision as of 02:56, 28 December 2023

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

[edit] 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.

[edit] Specifications

[edit] Software

[edit] Sample files

[edit] See also

[edit] Links

Retrieved from "http://fileformats.archiveteam.org/index.php?title=GEM_Raster&oldid=46691"
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