LibRaw technical support

Stable LibRaw versions: technical support, errors, API questions

How to use LibRaw for writing one's own demosaicking algorithm

Submitted by dolguldur on

Dear All, thank you very much for this really nice piece of opensource software !

I would like to write an inverse problem solver, that take as input multiple RAW files (taken from the same image), and outputs 3 RGB files for the image.
The way demosaicking is performed is up to me, but I would like to be able to rely on LibRaw in order to consistently know the mapping between each pixel coordinate (x_i, y_i) and its color channels (R,V or B), wether the input raw comes from cannon/nikon/sony/pentax,... .

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Getting SIG_SEGV in xtrans_decode_block (libraw_fuji_compressed.cpp)

Submitted by Torsten on

Hi Alex,

on my libraw port on android, I'm getting a SIGSEGV (signal 11 (SIGSEGV), code 2 (SEGV_ACCERR)) in the xtrans_decode_block function when trying to call "libraw_unpack" on a raf file reported by an user (X-T20)(see link below). What I tried is to check at which point exactly it crashes (it's a little tricky under android), and found out that it fails somewhere in the last loop (logged the state at line 712, the last output before it fails is:
xtrans_decode_block 22 15 512 (22 = g_even_pos, 15 = g_odd_pos, 512 = line_width)

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RAW to grayscale

Submitted by tfield98 on

I'm new to image processing.

I want to decode a raw image to produce a pgm file that has merged the 4 Bayer photosites with no pre-processing (like color balance, gamma, etc.) into a 16-bit grayscale pixel.

My first attempt was dcraw -4 -D which resulted in an image, but with the characteristic "blockiness" due to the unmerged photosites.

I know Libraw is based on dcraw code, so I thought I'd ask here if anyone has any suggestions on how to use dcraw in the above scenario.

Thanks!

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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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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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