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CR2 files are generated by Canon cameras, starting the 20D, 350D/Digital Rebel Xt and 1D. They supersede the older [[Canon CRW|CRW]].
# MIME type
image/x-canon-cr2
# Organisation
Canon CR2 files are TIFF files. All is organised in a TIFF / IFD file.
On of the differenciation with the CR2 files is that they have a header before the IFD0. This does not violate the TIFF spec.
[[!table header="no" class="mointable" data="""
**offset** | **length** | **description**
0 | 8 | TIFF header
8 | 2 | litteral 'CR'
10 | 1 | major version (2)
11 | 1 | minor version (0)
12 | 4 | (long) for the offset of the IFD3 that contain the RAW data. (in the TIFF byte order)
"""]]
Exif is attached to the ExifIFD of IFD0. The CFA data is in IFD3.
# Compression
Canon CR2 files use the old original [[Lossless_JPEG|Lossless_JPEG]] standard for the RAW data. The same used by [[Adobe DNG|Adobe DNG]].
Source: [[http://www.adobeforums.com/cgi-bin/webx/.3bc36454/0|http://www.adobeforums.com/cgi-bin/webx/.3bc36454/0]] (Dead link)
The width dimension specified in the JPEG stream is actually half the reality because it takes into account 2 channels per sample (the dimension of the CFA pattern).
350D, 5D and 30D files have a different layout. IFD3 (where the CFA is located) has the tag 0xc640 that contains 3 SHORT. 1, x, y. x is the number of column of the first "slice" of the image, y is for the second "slice".** I don't know what the 1 mean.**
The slicing means that the output scanlines have to be reorganised as they are shorter to have a top -> bottom then left -> right, a bit like columns of text. (TODO: do a nice diagram)
# Modified files
Apparently Canon's proprietary software modifies the RAW file. Other proprietary software seems to choke on said modified files ([[http://www.prophotohome.com/forum/raw-photo-processing-software-technique/62864-cr2-raws-converted-dpp-wont-open-aperture.html|http://www.prophotohome.com/forum/raw-photo-processing-software-technique/62864-cr2-raws-converted-dpp-wont-open-aperture.html]]).
[[ExifTool|ExifTool]] has some info:
* [[http://www.cpanforum.com/threads/1055|http://www.cpanforum.com/threads/1055]]
* [[http://www.cpanforum.com/threads/5170|http://www.cpanforum.com/threads/5170]]
# References
* [[http://lclevy.free.fr/cr2/|http://lclevy.free.fr/cr2/]]
* [[http://web.archive.org/web/20061125031802/http://crousseau.free.fr/imgfmt_raw.htm|http://web.archive.org/web/20061125031802/http://crousseau.free.fr/imgfmt_raw.htm]] (in French, by one of the developers of DxO)
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