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drewnoakes / metadata-extractor-dotnet

Extracts Exif, IPTC, XMP, ICC and other metadata from image, video and audio files
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General way to get thumbnail from any supported file format #127

Open Diddlik opened 6 years ago

Diddlik commented 6 years ago

Is there a way to get thumbnail from any file (jpeg, raw, mp4/mov) without reading whole file?

twest820 commented 6 years ago

Not sure which sense of any you're looking for but I posted some basic jpeg code for this in #35. A similar approach should work for most raw formats and I would expect mp4/mov, though this may be incorrect as I mostly work with avi. How much of the file actually gets read from disk is a somewhat complex function of the arguments to FileStream..ctor() and the metadata layout but, as a default starting point, you can expect load of at least one buffer's worth of data from the start of file.

See also #111.

Diddlik commented 6 years ago

it works, but not for all files. For example in Olympus RAW (*.orf) there are no ExifThumbnailDirectory...so its not possible to get information about offset and length of thumbnail.

twest820 commented 6 years ago

That's likely because Olympus chose not to conform to the EXIF standard when embedding thumbnails in their raws. You might try looking in the makernote.