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Cleaning up an image

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enxio27
Forum Member

Cleaning up an image

Post#1 by enxio27 » 22 Feb 2020, 02:12


Is there a fast way to clean up an image (after converting to black and white, and sometimes reducing in size) to smooth out the lines and make them more precise and sharp? Up to now, I have simply hand-edited the image, pixel by pixel, but that gets pretty tedious, especially for more complex images (I'm working on a few snowflakes at the moment). Any process that cuts down on that work, even if it doesn't eliminate it completely, would be very helpful. I'm using the images to make pattern files, so I want them to be as clean as possible. Finished size for each image ranges from about 150x150 pixels to 300x300 pixels.
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Wallace
Global Moderator

Post#2 by Wallace » 22 Feb 2020, 19:32


Cleaning up an image can mean many things.

Once the image(s) are converted to B&W.
Usually with a white background and the lines, or main subjects being black.

You can use color curves.
To help adjust the the white background and remove any stray pixels/anomalies from it.
While simultaneously tightening up the black lines as well.

For example:

Before applying Color Curves.
Screenshot (bfore).png
Screenshot (bfore).png (88.94 KiB) Viewed 6266 times
After applying Color Curves.
Screenshot (after).png
Screenshot (after).png (62.99 KiB) Viewed 6266 times
Image
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enxio27
Forum Member

Post#3 by enxio27 » 22 Feb 2020, 23:21


Wallace wrote:
22 Feb 2020, 19:32
Cleaning up an image can mean many things.

Once the image(s) are converted to B&W.
Usually with a white background and the lines, or main subjects being black.

You can use color curves.
To help adjust the the white background and remove any stray pixels/anomalies from it.
While simultaneously tightening up the black lines as well.
Already did that (evidently I wasn't clear--I'm sorry). I used Colors->Threshold to reduce it to black and white. Now I'm left with this (for example):
Winter-Frost-Large-Punch-Cartridge.png
Winter-Frost-Large-Punch-Cartridge.png (63.26 KiB) Viewed 6252 times
It still has a lot of jagged, asymmetrical edges that I want to smooth out and make symmetrical. I can edit the image pixel by pixel (and have, for some less complex images), but I'm hoping for a way to eliminate at least some of that tedium.
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Krikor
Forum Member

Post#4 by Krikor » 23 Feb 2020, 03:13


@enxio27 ,
Krikor - just one try
Krikor - just one try
qqname.png (119.21 KiB) Viewed 6248 times
Image obtained through these steps, authored by Ofnuts and Denzjos at: https://www.gimp-forum.net/Thread-Selec ... all-Specks

►Select the background color
►Select> Grow by one pixel
►Select> Shrink by one pixel
►[Delete]
►Filters / GMic-Qt / Black & White / Stamp
"I feel that in both art and music, it's not the success that matters but the pleasure it gives you. Focus on the pleasure and the learning will come naturally." - Brian Weston
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CtrlAltDel
Forum Member

Post#5 by CtrlAltDel » 24 Feb 2020, 10:16


Krikor wrote:
23 Feb 2020, 03:13

►Select the background color
►Select> Grow by one pixel
►Select> Shrink by one pixel
►[Delete]
►Filters / GMic-Qt / Black & White / Stamp
Hi, Krikor. Could you explain why you would grow by one pixel and then shrink by one pixel? I don't understand. Wouldn't shrinking it undo the growing that you just did? I tried following those instructions and it did not improve the image for me. What am I doing wrong?
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Krikor
Forum Member

Post#6 by Krikor » 24 Feb 2020, 14:12


CtrlAltDel wrote:
24 Feb 2020, 10:16
Krikor wrote:
23 Feb 2020, 03:13

►Select the background color
►Select> Grow by one pixel
►Select> Shrink by one pixel
►[Delete]
►Filters / GMic-Qt / Black & White / Stamp
Hi, Krikor. Could you explain why you would grow by one pixel and then shrink by one pixel? I don't understand. Wouldn't shrinking it undo the growing that you just did? I tried following those instructions and it did not improve the image for me. What am I doing wrong?
Hi @CtrlAltDel , I asked myself the same question when I saw these steps. It also made little sense to me. But coming from Ofnuts it was like having a guarantee seal.

So I tested these steps, but unlike you I was able to confirm that in fact small specks were actually eliminated.
As they are very small, I suggest checking the change with a zoom.

In the image below, the before and after using the first 4 steps (without applying the stamp filter).
Krikor - BeforeAfter - procedure to remove specks
Krikor - BeforeAfter - procedure to remove specks
beforeafter02.png (310.81 KiB) Viewed 6205 times
Note that I circled in red some spots that disappeared after the indicated procedure, but there are others that have not been marked but have also been removed.

Regarding the explanation behind this magic, I believe that when there is a 1 px magnification, the specks end up being selected along with the background color and form a unique selection. When the reduction is made by 1 px and after this selection is deleted, the specks are deleted along with the selection.

Similar to the footprints that are removed by the waves on the beach.
Image
But I suggest that the question be asked directly to @Ofnuts, he could better answer that question.
"I feel that in both art and music, it's not the success that matters but the pleasure it gives you. Focus on the pleasure and the learning will come naturally." - Brian Weston
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CtrlAltDel
Forum Member

Post#7 by CtrlAltDel » 24 Feb 2020, 22:36


Krikor wrote:
24 Feb 2020, 14:12
CtrlAltDel wrote:
24 Feb 2020, 10:16
Krikor wrote:
23 Feb 2020, 03:13

►Select the background color
►Select> Grow by one pixel
►Select> Shrink by one pixel
►[Delete]
►Filters / GMic-Qt / Black & White / Stamp
Hi, Krikor. Could you explain why you would grow by one pixel and then shrink by one pixel? I don't understand. Wouldn't shrinking it undo the growing that you just did? I tried following those instructions and it did not improve the image for me. What am I doing wrong?
Hi @CtrlAltDel , I asked myself the same question when I saw these steps. It also made little sense to me. But coming from Ofnuts it was like having a guarantee seal.

So I tested these steps, but unlike you I was able to confirm that in fact small specks were actually eliminated.
As they are very small, I suggest checking the change with a zoom.
I won't bother Ofnuts, you've explained probably as well as it needs to be explained. Thank you very much. I will try it again and see if I can gain a noticeable improvement with the image.

Thank you for such a detailed response.
GIMP Learn rocks...
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