Reading Raw Images

  • ImageMagick supports most RAW formats and provides Python bindings.

  • GraphicsMagick is the swiss army knife of image processing. GraphicsMagick is originally derived from ImageMagick 5.5.2 as of November 2002 but has been completely independent of the ImageMagick project since then.

  • dcraw is a raw image decoder written in C supporting many cameras.

  • LibRaw is a library for reading RAW files obtained from digital photo cameras (CRW/CR2, NEF, RAF, DNG, and others) with C++ API.

By default, dcraw alters the image brightness which we do not expect. Edit: dcraw has an option -W to disable auto brightening.

GraphicsMagick uses dcraw as a delegate. To change the settings, run gm convert -list delegate to find the path of your delegates.mgk, add options -6 -W -o 2 to the line for dcraw in that file. -6 for 16-bit depth, -W to disable auto brightening and -o 2 for Adobe RGB color space.

ImageMagick uses ufraw-batch as the delegate, whose default exposure compensation is set to 0, thus having no issue.

RAW Decoding Speed. dcraw is fast. gm is fast because it uses dcraw as a delegate. im is much slower.

FAQ

Q: delegate failed `"ufraw-batch"

A: Your ufraw-batch is too old. Update it with apt-get install ufraw.

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