Re: [Gimp-user] Need help repairing image

["Ronald F. Guilmette" <rfg tristatelogic com>]

Many thanks to both Steve Kinney and Daniel Smith for their various
suggestions for fixing this damaged color image.  I'm not sure that I
can do all the thinsg they've suggested, given my limited knowledge
of The Gimp at this point, or even that I understand them all, but I'm
going to go over all of them with a fine tooth comb and try to use
these ideas to educate myself more about The Gimp.  (It will be a good
learning experience.)

Meanwhile however, since my last post I came up with a cute idea myself
for doing the repair that may or may not actually fly, in practice.
(I haven't had time to really try it yet.)

I was reading about the clone tool and I found the "registered" mode,
you know, when you can copy corresponding pixels from one image to
the exact sorresponding point in another image, and that gave me an
idea...

Here's my idea in a nutshell... If I could make a "color inverted"
version of my damaged image... that is an image where all of the
luminance (brightness) levels are the same, pixel-for-pixel, as the
original, but where the colors are all inverted... so that magenta
becomes green and vise versa, and so forth... then I would have an
image where instead of a big green streak, I would instead have a
big magenta streak along the right hand side.  Then, my thought is
that I could perhaps use that "color inverted" image with the clone
tool... in registered mode... to gently "paint" some magenta-ness
from the right hand side of the color-inverted image over the top
of the green streak in the original image.  I could maybe do that
while using some low opacity value... like maybe 15% of something...
and then just keep on making strokes, a little at a time, until the
not-too-opaque strokes of magenta-ness exactly (or nearly exactly)
cancel out the unfortunate green-ness.

Well, I'm going to give that a try anyway.  It seems at least like
a plausible solution, in theory, even though it may not work in practice.
(I'll have to see about that.)

When I first came up with this idea, I thought that it might take some
serious fiddling and/or a brand new custom plug-in to get the kind of
"color inverted" image that I need for this experiment, but I was very
happily surprised (after a bit of googling) to see that Gimp already has
two facilities that, when combined, seem to give me exactly what I want
and need for this experiment.  Check it out!  Here again is the original:

   ftp://ftp.tristatelogic.com/private/gimp/img001-b.jpg

And here's what I came up with for a "color inverted" (but _not_ brightness
inverted) version of that:

   ftp://ftp.tristatelogic.com/private/gimp/img001-inverted.jpg

I created this latter version simply by using Gimp's color tool, and
applying two steps: (1) value invert, followed by (2) invert.

Seriously, just those two step gave me what I think I need, lickety split.
(Trivial really.)

I will report back here on the results from my experiment, when I get time
to complete it.

I am still really puzzled by one thing however.  Those two "invert" steps
from Gimp's color tool... I would have thought (naively?) that if one did
an "invert" followed by a "value invert" that you would have ended up with
the same image that you would get if you first did the "value invert" and
_then_ the plain invert.  But it seems not!  Far from it!  The above link
gives the image that resulted from doing value invert followed by invert.
Here is the image that was produced by doing the invert first, followed by
the value invert step:

    ftp://ftp.tristatelogic.com/private/gimp/img001-inverted2.jpg

Spooky!

Notice however that even in this very different "doubly inverted" image,
there is still quite a pronounced streak of magenta-ness along the right
hand side (which is, of course, what I wanted).

I suspect that if I try to do my cloning (registered, onto the original)
from the img001-inverted.jpg image, then that will have the effect of
increasing the contrast in the areas where I do that, whereas if I were
to try doing my registered cloing instead from the img001-inverted2.jpg,
then that would have the effect of decreasing the contrast in the areas
that I clone onto.

Since the green streak in the original is obviously an area of less than
ample contrast, I am most certainly going to try my experiment first using
the img001-inverted.jpg image (as a cloning source) rather than from the
img001-inverted2.jpg image.

You folks should all feel free to tell me that I'm crazy and/or wasting my
time with this experiment, if you think that's the case.  But I _am_ going
to give it a whirl.  Intutively, it just seems to be to be the Right Approach
to eliminate unwanted green-ness by neutralizing the green-ness with some
corresponding (but opposite) magenta-ness.

Now I just gotta go off and figure out how to do this.  I'm really not down
with this layers stuff yet.  Making a copy of an entire mage into a new
layer seems easy enough.  There's a button for that!  And I _think_ that
I understand how to look at the different layers one has created.  I just
don't know how to look at two or more layers on my screen all at once, you
in separate display windows.  (Maybe I don't even need to do that, but I
would feel more comfortable if I could see the thing I am cloning from _and_
the thing I am cloning to, all at once, in two windows on the same screen.)
how to view my new layer once I've got it

The one thing that worries me is that while I am netrializing the unwanted
green-ness, I do believe that I'll also and likewise be neturalizing the
color of the real underlying background rocks and snow.  But since... in
this image at least... the background snow is white and the background rocks
(luckily) happen to be mostly gray anyway, maybe my scheme for selective
"color neutralization" won't really hurt the backgound in any visually
unappealing way.  (Obviously, it would be a different story if, for example,
there were colorful flowers or a clown convention in the background.  Then,
drifing everything towards neutral shades of gray would be very unattractive.)

Regards,
rfg


P.S.  How does one just simply merge two images?  I'd really like to see
what my img001-inverted.jpg and img001-inverted2.jpg would look like if
they were smashed together.  (And actually, maybe the combination of those
two is the thing that I really want to be cloning from.)

Well, if nothing else I have at least learned how to make some really goofy
and/or spooky looking pictures with Gimp (using these "invert" features).
And that by itself is pretty cool.  That img001-inverted2.jpg kind-of
reminds me of my old days, 40 years ago, back in the darkroom when I used
to play around with "solarizing" prints.  What fun!  And now I don't even
need to get my hands wet, and don't need to spend time in a cramped tiny
little room, inhaling what were likely to have been at least slightly
toxic fumes from the developing chemicals.

It's slightly amazing to think that now, a whole generation has grown up,
or nearly so, never knowing the thrill of "real" protography, like in the
good old daze, when men were men, and when they walked around smelling like
fixer. :-)

(I love the smell of fixer in the morning.)