LibRaw technical support

Stable LibRaw versions: technical support, errors, API questions

Variable Contrast

Submitted by james on

Hi there,

I've been trying to use LibRaw on a project, but keep running into an issue where the output images don't look "contrasty" enough -- they differ substantially in contrast from both the embedded previews in the JPEG, as well as ACR and FastRawViewer (which I understood uses libraw internally?)

Looking in FRV, there's an option called "contrast curve type", which is set to "variable contrast" -- I think this is what I'm missing.

How do I invoke libraw such that it mirrors the "variable contrast" setting, so that my images look right?

Thanks!

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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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