Despeckling photos

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Despeckling photos

Luthien
I have several photos which I'd like to try to clean up as best I can. They all
have similar problems. They look like a bad copy of a black and white photo with
large amounts of speckling.

I'm not sure which tools to use. Should I use some combination of blurs or
masks?. Is there a particular tool that might be useful. Should the contrast be
adjusted?  I'm just looking to make minimal improvements. I know that I do not
have a lot to work with. Any suggestions would be appreciated.

Attachments:
* https://www.gimpusers.com/system/attachments/1309/original/despeckling.png

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Re: Despeckling photos

Users mailing list
There are a lot of options. What I have used most is Wavelet Decompose (see
here for an explanation -
https://pixls.us/articles/skin-retouching-with-wavelet-decompose/ ). I fix
old family photos that are usually full of scratches, etc.

This technique works, but note it takes a lot of time to work on each layer.

Check out more of Pat David's guides and YouTube where there are folks
who've posted videos for using GIMP. Best search terms are: enhance,
retouch, restore, fix, restoration, etc.

GuyS

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“Happiness is the meaning and the purpose of life, the whole aim and end of
human existence.”

― Aristotle

On Tue, Dec 3, 2019, 8:39 PM Gimp_Noob <[hidden email]> wrote:

> I have several photos which I'd like to try to clean up as best I can.
> They all
> have similar problems. They look like a bad copy of a black and white
> photo with
> large amounts of speckling.
>
> I'm not sure which tools to use. Should I use some combination of blurs or
> masks?. Is there a particular tool that might be useful. Should the
> contrast be
> adjusted?  I'm just looking to make minimal improvements. I know that I do
> not
> have a lot to work with. Any suggestions would be appreciated.
>
> Attachments:
> *
> https://www.gimpusers.com/system/attachments/1309/original/despeckling.png
>
> --
> Gimp_Noob (via www.gimpusers.com/forums)
> _______________________________________________
> gimp-user-list mailing list
> List address:    [hidden email]
> List membership: https://mail.gnome.org/mailman/listinfo/gimp-user-list
> List archives:   https://mail.gnome.org/archives/gimp-user-list
>
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Re: Despeckling photos

Liam R E Quin
In reply to this post by Luthien
On Wed, 2019-12-04 at 03:39 +0100, Gimp_Noob wrote:
> I have several photos which I'd like to try to clean up as best I
> can.

First, scan at higher resolution than yu plan to use. At least double.

SOmetimes i find that select by colour works well.
(1) make sure you have both blacks andwhites in your image, e.g. with
levels or curves.
(2) select by colour on a white area.
(3) grow selection e.g. 2 pixels
)4_ shrink selectin by 2 pixels
(6) feather by 1 pixel (requires greyscale or RGB iamge, not indexed)
(7) fill with white (e.g. drag the swatch from the toolbox, or use
control-. or control-,)
(8) select none

repeat steps 2 to 8 with black instead of white.

slave liam


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with fabulous vintage art and fascinating texts to read.
Click here to have the slave beaten.

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Re: Despeckling photos

Gary Aitken-2
On 12/4/19 1:44 AM, Liam R E Quin wrote:

> On Wed, 2019-12-04 at 03:39 +0100, Gimp_Noob wrote:
>> I have several photos which I'd like to try to clean up as best I
>> can.
>
> First, scan at higher resolution than yu plan to use. At least double.
>
> SOmetimes i find that select by colour works well.
> (1) make sure you have both blacks andwhites in your image, e.g. with
> levels or curves.
> (2) select by colour on a white area.
> (3) grow selection e.g. 2 pixels
> )4_ shrink selectin by 2 pixels
> (6) feather by 1 pixel (requires greyscale or RGB iamge, not indexed)
> (7) fill with white (e.g. drag the swatch from the toolbox, or use
> control-. or control-,)
> (8) select none
>
> repeat steps 2 to 8 with black instead of white.

Can you explain what steps 3 and 4 acconplish?  It seems like they should
cancel each other.

Gary
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Re: Despeckling photos

Liam R E Quin
On Wed, 2019-12-04 at 09:32 -0700, Gary Aitken wrote:
> On 12/4/19 1:44 AM, Liam R E Quin wrote:
> > On Wed, 2019-12-04 at 03:39 +0100, Gimp_Noob wrote:
> > >
> > (2) select by colour on a white area.
> > (3) grow selection e.g. 2 pixels
> > )4_ shrink selectin by 2 pixels

> Can you explain what steps 3 and 4 acconplish?  It seems like they
> should cancel each other.

Consider a black speckle that's a square 4 pixels wide and high (for an
example).

The selection goes to the edge of the speckle, all round.

Growing the selection by 2 pixels will make the marching ants meet in
the middle of the speckle - but there are no pixels of it left outside
the selection, it'snow fully selected.

Shrinking the selection won't create holes, so the tiny speckles are
gone.

Experiment using 1 pixel instead of 2, or grow by 2, shrink by 1,
feather by 1 or 2, making sure you don't lose too much detail.

In practice i scan in greyscale, not black and white, so it also
depends on the "threshhold" paraneter in the select-by-colour tool as
to how close the the speckles the selection goes, but i use Curves
first to brighten the hilights somewhat and to darken the shadows. If
you are working with a film rather than something printed in a book,
that may not be appropriate - in that case, it helps to have the image
in Precision 16 integer of 32 floating point (from the Image/Precision
menu) so that you don't lose detail as you work.

Hope this helps,

slave


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Despeckling photos

Luthien
>Consider a black speckle that's a square 4 pixels wide and high (for
>an
>example).
>
>The selection goes to the edge of the speckle, all round.
>
>Growing the selection by 2 pixels will make the marching ants meet in
>the middle of the speckle - but there are no pixels of it left outside
>the selection, it'snow fully selected.
>
>Shrinking the selection won't create holes, so the tiny speckles are
>gone.
>
>Experiment using 1 pixel instead of 2, or grow by 2, shrink by 1,
>feather by 1 or 2, making sure you don't lose too much detail.
>
>In practice i scan in greyscale, not black and white, so it also
>depends on the "threshhold" paraneter in the select-by-colour tool as
>to how close the the speckles the selection goes, but i use Curves
>first to brighten the hilights somewhat and to darken the shadows. If
>you are working with a film rather than something printed in a book,
>that may not be appropriate - in that case, it helps to have the image
>in Precision 16 integer of 32 floating point (from the Image/Precision
>menu) so that you don't lose detail as you work.
>
>Hope this helps,
>
>slave
Thanks.

What should I do if I only have a .jpg file? In other words,there is nothing to
scan. If I remove too many speckles it looks fake.


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Re: Despeckling photos

Liam R E Quin
On Fri, 2019-12-20 at 21:12 +0100, Gimp_Noob wrote:
> What should I do if I only have a .jpg file? In other words,there is
> nothing to scan. If I remove too many speckles it looks fake.

There's no simple answer - you have to d the best you can with what
you've got. Sometimes resizing (image->scale) by a factor of 3 can
help: open image->scale image, append
  * 3
to the width
and press tab, and GIMP will do the multiplication :) Use "cubic"
interpolation.

Then blur the now-larger image with radius 5. Then scale back down
(again cubic but you could use / 3 instead of * 3 to have GIMP do the
division) and then sharpen (filters->enhanve/>unsharp mask).

Technically what's going on is that this procedure will give the image
a wider number of pixel values - more greys - especially in 16 or 32
bit - and reduce some of the effects of jpeg artifacts.  <ale sire the
image is in greysvcale/grayscale or RGB mode first, not indexed, or it
won't help.

--
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with fabulous vintage art and fascinating texts to read.
Click here to have the slave make breakfast.

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Despeckling photos

Luthien
>There's no simple answer - you have to d the best you can with what
>you've got. Sometimes resizing (image->scale) by a factor of 3 can
>help: open image->scale image, append
>  * 3
>to the width
>and press tab, and GIMP will do the multiplication :) Use "cubic"
>interpolation.
>
>Then blur the now-larger image with radius 5. Then scale back down
>(again cubic but you could use / 3 instead of * 3 to have GIMP do the
>division) and then sharpen (filters->enhanve/>unsharp mask).
>
>Technically what's going on is that this procedure will give the image
>a wider number of pixel values - more greys - especially in 16 or 32
>bit - and reduce some of the effects of jpeg artifacts.  <ale sire the
>image is in greysvcale/grayscale or RGB mode first, not indexed, or it
>won't help.

I  lost some detail on the edit, but I got rid of a lot of the noise thanks.

Attachments:
* https://www.gimpusers.com/system/attachments/1335/original/despeckling.png
* https://www.gimpusers.com/system/attachments/1336/original/despeckling-edit.png

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