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