[digiKam-users] Strange Editor Rendering

Gilles Caulier caulier.gilles at gmail.com
Thu Mar 15 11:10:21 GMT 2018

The Impulse Denoise option give artifacts. The Exposure correction amplify
this side effect.

It's certainly a problem in libraw GPL3 extension pack. We do not process
anything in DK Raw import tool while demosaicing.

I try to reproduce the dysfunction with the libraw command line tool to
preform demosaicing (the option are similar than dcraw CLI tool).
If you have compiled yourself DK, all libraw CLI tools are in
core/test/rawengine/. dcraw_emu is the tool to reproduce all operations on
command line :

[gilles at localhost rawengine]$ ./dcraw_emu
dcraw_emu: almost complete dcraw emulator
Usage:  ./dcraw_emu [OPTION]... [FILE]...
-c float-num       Set adjust maximum threshold (default 0.75)
-v        Verbose: print progress messages (repeated -v will add verbosity)
-w        Use camera white balance, if possible
-a        Average the whole image for white balance
-A <x y w h> Average a grey box for white balance
-r <r g b g> Set custom white balance
+M/-M     Use/don't use an embedded color matrix
-C <r b>  Correct chromatic aberration
-P <file> Fix the dead pixels listed in this file
-K <file> Subtract dark frame (16-bit raw PGM)
-k <num>  Set the darkness level
-S <num>  Set the saturation level
-R <num>  Set raw processing options to num
-n <num>  Set threshold for wavelet denoising
-H [0-9]  Highlight mode (0=clip, 1=unclip, 2=blend, 3+=rebuild)
-t [0-7]  Flip image (0=none, 3=180, 5=90CCW, 6=90CW)
-o [0-6]  Output colorspace (raw,sRGB,Adobe,Wide,ProPhoto,XYZ,ACES)
-j        Don't stretch or rotate raw pixels
-W        Don't automatically brighten the image
-b <num>  Adjust brightness (default = 1.0)
-q N      Set the interpolation quality:
         0 - linear, 1 - VNG, 2 - PPG, 3 - AHD, 4 - DCB
-h        Half-size color image (twice as fast as "-q 0")
-f        Interpolate RGGB as four colors
-m <num>  Apply a 3x3 median filter to R-G and B-G
-s [0..N-1] Select one raw image from input file
-4        Linear 16-bit, same as "-6 -W -g 1 1
-6        Write 16-bit linear instead of 8-bit with gamma
-g pow ts Set gamma curve to gamma pow and toe slope ts (default = 2.222
-T        Write TIFF instead of PPM
-G        Use green_matching() filter
-B <x y w h> use cropbox
-F        Use FILE I/O instead of streambuf API
-timing   Detailed timing report
-fbdd N   0 - disable FBDD noise reduction (default), 1 - light FBDD, 2 -
-dcbi N   Number of extra DCD iterations (default - 0)
-dcbe     DCB color enhance
-aexpo <e p> exposure correction
-apentax4shot enables merge of 4-shot pentax files
-apentax4shotorder 3102 sets pentax 4-shot alignment order
-dbnd <r g b g> debanding
-mmap     Use mmap()-ed buffer instead of plain FILE I/O
-mem       Use memory buffer instead of FILE I/O
-disars   Do not use RawSpeed library
-disinterp Do not run interpolation step
-dsrawrgb1 Disable YCbCr to RGB conversion for sRAW (Cb/Cr interpolation
-dsrawrgb2 Disable YCbCr to RGB conversion for sRAW (Cb/Cr interpolation
-disadcf  Do not use dcraw Foveon code even if compiled with

But the impulse denoise option is not here. Only the wavelets denoise
exists, and this one work fine in DK (as with CLI tool).

As it said in libraw site, the libraw extra extension pack GPL2 and GPL3
are deprecated with next libraw 0.19. So i suppose that reporting this
problem to libraw team will be not supported as well.

Gilles Caulier
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