On 12/26/2011 05:14 AM, Ronald F. Guilmette wrote:
> The following file was generated from a recent scan of a 40 year old
> 6x7cm color negative:
>   ftp://ftp.tristatelogic.com/private/gimp/img001-b.jpg
> [...]
> I'd very much appreciate any advice that anybody would like
> to share with me about this image.  Obviously, my goal is to get rid of
> the green stripes while (if possible) still preserving as much of the
> underyling image detail in the discolored parts of the image as possible.
> (As you can see, there is really quite a lot of image detail underneath
> those green streaks.)
> I tried, briefly, using Gimp's built-in "destripe" function, but that
> really didn't seem to help much, no matter how I played with the relevant
> sliders.

Hey Ronald,

You won't find a "one tool" or "one filter" solution for this one. 
This is a fairly major project.  However, rest assured it can be
done; check out the first image on this page: 
http://pilobilus.net/photo_rework.html  It's far from perfect but
not bad for something I did ten or so years ago with an earlier
version of the GIMP, and demonstrates something of what is possible.

You face three problems:  An unwanted color, an unwanted darkening,
and loss of detail.  The fact that the areas that need the most work
are landscape background is a Good Thing, as you can afford to alter
a lot of detail in the affected areas without losing "important"
visual information. 

First, save your original image as a .xcf file.  You will be working
on this over several sessions, most likely, and you will need all
the "state" of the image - layers, etc. - intact in the saved
image.  Every time you have a new bright idea for how to fix part of
the image, either save your image then save it with a new name (i.e.
with an incremented version number), or create a brand new layer and
work on that.  This will protect the satisfactory elements of your
progress from mishaps.

You might want to start by doing what you can with filters. 
Duplicate your base layer, and select the damaged area.  Turn on
your Colors > Hue / Saturation tool, click on the image, and in the
dialog box that appears, select green and dial the saturation down
and brightness up until most of the green disappears.  This will not
fix the image but it carries you part of the way there.

Then you might want to "select none" and get busy with the Clone and
Smudge tools, painting in replacements for the "lost" areas, guided
by (but not strictly limited to) the content of the partially
restored area.  This is what I managed in three or four minutes,
nowhere near done of course:


As always, there are MANY ways to do things, and you might be able
to come much closer to a final repair by using multiple layers,
gradient masking, colormap rotation and other advanced filters,
etc.; but the above will at least give you lots of exercise with the
clone and smudge tools, brush usage, etc., and will (eventually!)
give you an image that looks good.

For a beginner this is a fairly major hobby project, but as such it
is a great training exercise.  Play around, find out what tools do
what things, and bear in mind that the objective at this stage is
not an image that "is right" in the sense of an exactly faithful
reproduction of the original scene, but an image that "looks right"
in the sense that it conveys the general appearance of the scene to
the viewer.



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