On Wed, Dec 21, 2016 at 11:27 AM, J. Liles <malnour...@gmail.com> wrote:
> > > On Wed, Dec 21, 2016 at 11:20 AM, J. Liles <malnour...@gmail.com> wrote: > >> >> >> On Wed, Dec 21, 2016 at 11:17 AM, Ingo Liebhardt <ingo.liebha...@ziggo.nl >> > wrote: >> >>> Ah, and by the way @J Liles: could you please explain me a bit more what >>> you mean by ‚textile like artifact‘, I’d like to investigate that one a bit >>> more in-depth. >>> Thx >>> >>> >>> Am 21.12.2016 um 20:10 schrieb Ingo Liebhardt <ingo.liebha...@ziggo.nl>: >>> >>> Hi all, >>> >>> Thanks a lot for the feedback, and no worries if it takes you a while >>> testing it. >>> As you see, I’m also progressing rather slowly on my side… >>> >>> It’s still a proof-of-concept and I have quite some items on my to do >>> list, most notably: >>> - the literature mentions training the filters based on reference >>> images, and I’m slowly working on this, hoping that it would further >>> increase image quality. So far, the filters are designed using the window >>> design method. >>> - trying to find out where the hue shifts come from - I already noticed >>> them, too. >>> >>> Other things like performance improvements will be for later… >>> >>> I’ll let you know as soon as I make progress on the filters. >>> >>> Cheers, >>> Ingo >>> >>> >>> >>> Am 21.12.2016 um 01:14 schrieb J. Liles <malnour...@gmail.com>: >>> >>> >>> >>> On Mon, Dec 19, 2016 at 7:40 PM, J. Liles <malnour...@gmail.com> wrote: >>> >>>> >>>> >>>> On Mon, Dec 12, 2016 at 10:40 AM, Ingo Liebhardt < >>>> ingo.liebha...@ziggo.nl> wrote: >>>> >>>>> Hi all, >>>>> >>>>> Maybe you still remember that I tried an alternative approach to >>>>> X-Trans demosaicking (using guided filtering) in March / April this year… >>>>> In the end, I was not satisfied, and I gave up on that approach. The >>>>> problems were comparable to the Markesteijn algorithm, and the >>>>> improvements >>>>> marginal. >>>>> >>>>> After giving up on that approach, I was again browsing conference >>>>> papers trying to get some inspiration. >>>>> I came across the work of E. Dubois, which looked promising. >>>>> It is promising, not so much when applied alone, but very much so when >>>>> combined with a gradient based approach like Markesteijn. >>>>> >>>>> I like Jo’s xtrans fringes profile a lot, but the colors get somewhat >>>>> muted, overall. >>>>> >>>>> Contrary to my first approach, this one finally seems to give >>>>> reasonable results. >>>>> I managed to get good output for the redline bug #10333. >>>>> You can have a look here: dropbox link >>>>> <https://www.dropbox.com/sh/un1y11uimbqxjjk/AAD3L-Rs9-ztwyBIm4rnCzK-a?dl=0> >>>>> >>>>> This is the output just with demosaic + base curve, nothing else. >>>>> >>>>> If you want to try some nasty X-Trans images yourself, I made a little >>>>> proof-of-concept. >>>>> This in form of a fork of darktable, which you can find here: >>>>> https://github.com/ILiebhardt/darktable.git >>>>> For trying, just compile, deactivate openCL (only C code thus far), >>>>> and choose ‚1 pass Markesteijn‘ as demosaicking method (doesn’t work for >>>>> 3-pass, and wouldn’t really yield advantages, either). >>>>> >>>>> Have fun trying, and let me know if you think that this one’s worth >>>>> pursuing further (only quick hack so far, and the used correlation filters >>>>> are a slow, naive implementation O(m n p q)). >>>>> >>>>> If you’d like to read some basics concerning the idea, I made a >>>>> mini-blog here: http://xtransdemosaicking.blogspot.nl >>>>> >>>>> Cheers, >>>>> Ingo >>>>> >>>>> >>>>> P.S.: concerning my previous approach, J Liles spotted single >>>>> pixel artifacts. I found out that these are not related tot the >>>>> demosaicking as such. X-Trans 2 and X-Trans 3 have hybrid AF, and the >>>>> pixels used for phase detection show higher noise. These are all green >>>>> pixels of a 4-group of pixels; never a red or blue, and never a solitary >>>>> green. But solving this would be a whole different project... >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> ___________________________________________________________________________ >>>>> darktable developer mailing list to unsubscribe send a mail to >>>>> darktable-dev+unsubscr...@lists.darktable.org >>>>> >>>> >>>> Ingo, >>>> >>>> Great to hear you're still working on this! >>>> >>>> I haven't reviewed the code of the algorithm, but I did give it a try >>>> on a few images. >>>> >>>> Here's one in particular (lots of sharpening added to make the >>>> differences more obvious.) >>>> >>>> http://www.nevermindhim.com/liebhardt-test >>>> >>>> Direct image links: >>>> >>>> http://www.nevermindhim.com/files/liebhardt-test/6acffe60-09 >>>> c5-11e6-93d7-178612e3e7eb_E1_VNG.png >>>> http://www.nevermindhim.com/files/liebhardt-test/6acffe60-09 >>>> c5-11e6-93d7-178612e3e7eb_E1_Markesteijn.png >>>> http://www.nevermindhim.com/files/liebhardt-test/6acffe60-09 >>>> c5-11e6-93d7-178612e3e7eb_E1_Liebhardt.png >>>> >>>> >>>> My first impressions are: >>>> >>>> 1) (obviously you know this) It's slow >>>> 2) It introduces a hue shift >>>> 3) It does a better job of controlling color noise than VNG or >>>> Markesteijn. >>>> 4) Artifacts are similar in structure to Markesteijn (maze-like) >>>> 5) There is an additional textile like artifact that Markesteijn >>>> doesn't exhibit. >>>> 6) It overshoots in interpolating across gradients, but not as much as >>>> VNG does. >>>> >>>> If you can get rid of the textile effect and, color cast, and speed it >>>> up, this looks like it would be an improvement over Markesteijn (with no >>>> color smoothing/noise reduction). It's already looking more "film like" >>>> >>>> >>>> >>> Replying to myself here... >>> >>> Added another set of images to: >>> >>> http://www.nevermindhim.com/liebhardt-test >>> >>> (TEST IMAGE 2) >>> >>> This time correcting for the hue shift (with auto white balance). >>> >>> I wanted to illustrate how it deals with a high ISO (12800) image, with >>> and without noise reduction and sharpening. >>> >>> As you can see, the result is a definite improvement, especially the >>> noise reduced version. There may be a slight loss of sharpness, but for me >>> it's worth it to get rid of those crusty false colors. >>> >>> However, whether or not even this is better than the SOOC JPEG (NR -4, >>> Sharpness 0) is debatable. It seems like using the maximum NR in darktable >>> is required to produce a similar result as the minimum NR in camera... >>> >>> >>> >>> ___________________________________________________________________________ >>> darktable developer mailing list to unsubscribe send a mail to >>> darktable-dev+unsubscr...@lists.darktable.org >>> >>> >>> >> In TEST IMAGE 1, look at the blue TV screen behind the subject's head. >> You can see a textile/grid type effect that wasn't really there. This >> effect doesn't appear with VNG or Markesteijn. It looks like the your >> weightings might be off causing the X-Trans pattern to show through when >> interpolating solid colors. >> >> > Just to add to this, other points of interest in this image for finding > artifacts are the saturated purple lights in the upper right, and the edges > of the TV screen and the subject's hair. Of particular interest is the > serial number on the dollar bill. It should be dark green (the same color > as the stamp/seal above). Too-aggressive chroma denoising may make it turn > light gray/green like the rest of the bill. > > Continuing my habit of replying to myself, I was curious how your algorithm would handle the dreaded X-Trans II/III "purple flare/grid artifact" problem (which, AFAICT, remains an unsolved problem everywhere). The result is interesting. Your algorithm completely removes the purple color cast of the flare, resulting in, IMHO, a much more pleasing appearance. However, the grid aspect remains: http://www.nevermindhim.com/files/liebhardt-test/a75767d6-cc7c-11e6-95bd-739c86278d6a_E1_Liebhardt.png ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
