Re: [Gimp-user] New User Need Help Enlarging/Enhancing Image

[Matthew Woehlke <mwoehlke floss gmail com>]

On 2018-08-13 15:01, nickib wrote:
> > You might be going about this all wrong. If you really want to use
> > this to produce a very large physical print, I would consider 
> > embracing that the original image is smudgy by upsampling it (maybe
> > to 7200x3600 if not 14400x7200 after cropping it to 2:1) and then 
> > applying some of gimp's artistic filters to achieve a look that is
> > more "painting" than "photograph".>
> Matthew - and all of you really - I am blown away by all of your knowledge and
> comprehension of this dilemma and possible solutions!  I SO WISH I could
> understand the language and techniques better!  I might as well be staring at
> the GIMP program in Japanese for as much as I am lost!  At the risk of
> sounding like a complete idiot can any of you recommend how I might go about
> figuring out these ideas or where I might go for assistance in doing so?

The more I look at the "lightroom version", the less I like it. For me,
the orange is oversaturated; I preferred the softer, more "pastel" look
of the original. Also, the dock is so dark in the original that trying
to recover any detail there doesn't look particularly good to my eye,
besides that I preferred it being just a silhouette anyway.

I also looked at how I would crop it to 2:1 and... didn't like any of
*those* results either. You either lose a lot of the interesting bits of
the sky, or the interesting detail on the sand in the lower corner, or
both. If you can keep the original aspect ratio, it might be worth doing so.

I decided to play around with it, and came up with this:
JPEG:
https://drive.google.com/file/d/16LIjBfkghhJr-A-6eDQCmlqTAe1mhRVv/view?usp=sharing
XCF: https://drive.google.com/open?id=12Kp1HUB1tlQNgk2LzQSSh3vcrQg-3lYM

(I crushed the quality rather severely on the JPEG to get the file size
down. This is meant as a preview only; the XCF is lossless and includes
all of the layers that were used to achieve this composition.)

This reflects how I often process images in order to enhance local
contrast, although I usually throw in one or two mantiuk06 layers as well.

- The "equalize contrast" layer is the original, desaturated (I almost
always use luminosity mode), inverted, and then with a Gaussian blur
applied (which I forget to do this time, but the other layers hammer the
values enough that it doesn't matter in this case). Without the blur,
this will tend to wash out the value range entirely in your image,
leaving you just color. *With* the blur, it will reduce global contrast
while retaining local contrast; basically, it's a sort of "poor man's
HDR" that will bring back details in your shadows and highlights. In
this case, however, it didn't work very well, though it does keep the
light areas in the clouds from washing out quite so badly.

- STRESS (Tools → GEGL Operation) is just fun. Not only will it help
your contrast, it has an uncanny ability to remove color bias. Lower
radius and iterations give more local contrast but are also more prone
to noise and artifacts. I usually like to use one layer with the radius
and iterations as low as possible as a gentle (low opacity) overlay
(i.e. the "overlay" blending mode) to enhance contrast, and another with
the radius cranked up (the recommendation is "longest image dimension"
­— in this case, 4000 — or the max of 5000) and 15+ iterations as an
overall "improvement" layer that I usually blend in heavily or just
outright replace the original image at the bottom of the stack.

- C2G (also GEGL) is basically STRESS without the color. I've started
more recently using this as an additional overlay layer, as dropping the
color often lets me get away with using a lower radius without the
resulting artifacts being as bad. In this instance, I thought it made
the shadows on the waves *too* dark, so I added a layer mask to blend it
out toward the bottom.

- After playing with the blending on the above to get the contrast I
liked, the sky was *too* blue, so I cloned the original and applied it
with "color" blend mode to bring back some, but not all, of the pink.
Per above, I personally think *some* blue gives character to the result,
especially thinking of it as a painting and not something trying to be
perfectly realistic. However, you could play with the opacity on this
layer to bring the colors more back toward the original, or also play
with Colors → Hue-Saturation (or maybe Colors → Curves) if you like a
more saturated look.

I stopped at this point, which basically represents where I felt
satisfied with the overall color and contrast. Per my previous
suggestion, however, what I would do from here is to save this, then
start a new image from 'copy visible', scale it up to your desired
size/DPI, then play around with Oilify, Van Gogh, and/or Gimpressionist
(or really anything under Filters → Artistic). For this piece, I felt
the best results from gimpressionist were obtained setting the stroke
direction and size both to 'adaptive', setting the brush relief to 0,
and cranking the density. You'll also almost certainly want 'evenly
distributed' placement. In any case, be warned that some of these may
take quite a while to run at high resolution; you may want to play
around for a while on a few small sections of the image.

-- 
Matthew