#163 exif support for raw from 300d

[Tomasz Golinski]

Now, gqview shows exif information from raw only for
some cameras, e.g. 20d, 5d. With raw files from 300d
there is no exif information.

I suppose there are two solutions: either use exif from
crw file (eg. by code from crwinfo) or hack it to grab
exif from accompanying .thm files (in fact - plain jpg).

If needed, I can attach sample photos.

[John Ellis]

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Well, it has been a while since I was in the canon support
code of GQview (format_canon.c), but there was some
discussion on the gqview-devel mailing list a while back
(when the existing support was added).

CRW does not use the same format as CR2 files for the 'EXIF
data', if I remember correctly the data is in canon's own
implementation of an EXIF-like format.

Someone will have to fix what's there and/or implement it to
be able to parse the CRW data (they would basically be
implementing another exif-like parser for GQview).

[Jon Senior]

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I have the same camera and the same problem. A little investigation using downloaded test raw files shows that the problem is with .crw files. The CR2 files from newer Canon cameras decode fine. The difference is thus between the "cr2" routines and the "crw" ones.

[Jon Senior]

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Sorry. Didn't notice the comments already posted. With regard to a parser, dcraw.c (Dave Coffin's glorious raw decoder) contains an apparently self-contained CIFF parser. I would attach the relevant code, but I can't work out how to other than copy+paste. It seems to work using just the offset of the data and the length of the data (Which he defines as the file length - the offset). From there it recursively loads specific information which interests him into various variables. I'll take a look at GQView and see how easy it would be to just change his variables for yours.