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. ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to darktable-dev+unsubscr...@lists.darktable.org
