LibRaw technical support

Stable LibRaw versions: technical support, errors, API questions

L* gamma

Submitted by Explorus on

Is there a way to specify libraw to use the L-star gamma function? Or do I need to manually apply the function, and then specify the libraw linear function?
I mean this formula (from lindblum.com): (linear <= (216.0 / 24389.0)) ? (linear * 24389.0 / 2700.0) : (1.16 * Math.pow(linear, 1.0 / 3.0) - 0.16);

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How to compile LibRaw with RawSpeed?

Submitted by Kuro on

I've been using LibRaw 0.18.3 with success.

Now I want to add support for RawSpeed. I read that FastRawViewer is using RawSpeed. So how do I get RawSpeed support in LibRaw 0.18.3?

I've been trying all weekend without success. I can get it to compile, but in the linking stage, it always comes back with error on "-lrawspeed". Since RawSpeed is not a library, I'm not sure why the Makefile.dist has this as an option?

I'm using RawSpeed at the master branch.

Can anyone help?

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Instanciate the libraw class in c#

Submitted by NicolasB on

Hi, I try to work with libraw in my c# project. (Very new with c, c++ ...)
I can convert a raw image to ppm easily with this:

var dataPtr = NativeMethods.libraw_init(LibRaw_constructor_flags.LIBRAW_OPIONS_NO_DATAERR_CALLBACK | LibRaw_constructor_flags.LIBRAW_OPIONS_NO_MEMERR_CALLBACK);

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RGB color transformation

Submitted by ErwinL on

When I let DCRAW apply demosaicing, a color transformation based on the rgb_cam matrix is carried out in convert_to_rgb().
This transformation (within sRGB color space) gives my images a warm and slightly greenish look, which is not present in accompanying JPGs (taken with 'sunny' color balance).
For my camera, a Canon EOS 1100D, I found the rgb_cam matrix to be filled in by the adobe_coeff() function.
Should I really use this transformation? Or is there a better way to correct the cross-sensitivity of the color filters?

Erwin

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Canon - offset in color filter array

Submitted by konradm on

Hi,

When I use image demosaicing with color filter array got by LibRaw::COLOR(row, column) most outputs looks consistent apart from some Canon images, which looks too purple.
For those files obtained color filter array (by COLOR(row, col)) looks like simple RGGB:
R G
G B
However if I use row offset instead:
G B
R G
the results seems to be OK.
Does LibRaw return correct cfa pattern for those files?

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In-Depth Demosaicing Algorithm Analysis

Submitted by Falka on

At the completion of a project that uses LibRaw, I want to share the more intense algorithm artifact analysis to be helpful for anyone hoping to use LibRaw in the future, and as a thank-you to Alex for the direct support.

To summarize, algorithm (user_qual) 11, DHT, is the best. It's better than the best offered by RawTherapee, too.
Here are the most important examinations I performed!

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Number of colors in bitmap thumbnail

Submitted by konradm on

Hi,

I noticed that for .dng files with bitmap thumbnail LibRaw claims that there is no color in the preview (thumbnail.tcolors = 0 after open_file() + unpack_thumb()).
Shouldn't it return 3 colors (tcolors = 3) as from documentation LIBRAW_THUMBNAIL_BITMAP preview contains RGB bitmap?

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Extracting Metadata Without Unpacking RAW Data

Submitted by kennyc on

Is there a way to have libraw extract the metadata from a RAW file without unpacking all the data?

I'm using the libraw plug-in that is part of OpenImageIO. In that plugin, unpack() is called before any of the image properties are read, which causes the property reading to be incredibly slow because unpacking() is slow (relative to just reading the TIFF header in most RAW files.)

https://github.com/OpenImageIO/oiio/blob/master/src/raw.imageio/rawinput...

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