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Seeking better "green screen" method

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Seeking better "green screen" method Jay Smith 17 Jan 20:17
  Seeking better "green screen" method Chris Mohler 17 Jan 20:29
   Seeking better "green screen" method Jay Smith 17 Jan 20:52
    Seeking better "green screen" method Chris Mohler 17 Jan 21:05
     Seeking better "green screen" method Willie B Bass 17 Jan 21:06
      Seeking better "green screen" method Patrick Shanahan 17 Jan 21:42
   Seeking better "green screen" method Seth Burgess 17 Jan 21:01
  Seeking better "green screen" method Liam R E Quin 17 Jan 20:53
  Seeking better "green screen" method Liam R E Quin 17 Jan 20:54
  Seeking better "green screen" method Steve Kinney 17 Jan 23:47
  Seeking better "green screen" method Rob Antonishen 18 Jan 00:28
Seeking better "green screen" method Judah Kleinveldt 18 Jan 07:25
Jay Smith
2012-01-17 20:17:14 UTC (over 2 years ago)

Seeking better "green screen" method

Hi,

Gimp 2.6.6 on Ubuntu Linux 8.04.

Scanning using VueScan Professional 8.5.20 with an "Epson Perfection 4490 Photo" scanner. Color profile has been built for the scanner using available photo color target from a well-known German source (can't remember name).

Almost all my scanning is of postage stamps and related items -- scanning the actual physical objects, not photos of the objects.

Problem:

The stamps are currently scanned on a black background (for lack of other color possibilities; the final goal is on a black background). After scanning, the background is selected and turned to 100% black to have greatest contrast for the object. When a stamp has a postmark that crosses the edge of the stamp paper, the color of the postmark (usually dark or black) is very close to the color of the scanning background and thus when the background is selected, the selection "leaks" and "follows" the postmark onto the stamp. We have to manually exclude those "leaks" from the desired selection area.

Goal:

To be able to select the background (for change to 100% black) without any "leakage" of the selection onto the stamp objects AND without ANY non-black color artifacts remaining after changing the selection to 100% black.

Attempted Solutions:

We have tried scanning on many different non-black background colors and surfaces, but there are always some extreme-edge color artifacts remaining ... leaving a sort of "halo" effect around the stamp object.

Some of this could be attributable to the particular model of scanner, though every scanner I have ever owned had a similar problem to a greater or lesser degree. The width of the "halo" usually depends upon which side of the object it is on vs the direction of travel of the scanner device.

In television broadcasting it is extremely common for somebody to stand in front of a "green screen" and for the green to be electronically replaced with some image or video, etc. (For example, the weather person standing in front of a weather map.) It is rare to see a green "halo" if everything has been done correctly and if the person is wearing the correct type of clothing fabric.

Is there some Gimp method or plug-in or other tool that will better handle this type of use?

Recently poster Ron Guilmette discussed his use of "Darla-PurpleFringe.scm" plug-in to remove an artifact caused by a digital camera and subsequent processing.

Is there something like that which can be used to remove a color "halo" that results from using a "green screen" approach to scanning? (I would likely have to select different colors of "green screen" so that such colors are not included in the design of the postage stamp.

Any advice would be appreciated.

Jay

Chris Mohler
2012-01-17 20:29:50 UTC (over 2 years ago)

Seeking better "green screen" method

On Tue, Jan 17, 2012 at 2:17 PM, Jay Smith wrote:

Goal:

To be able to select the background (for change to 100% black) without any "leakage" of the selection onto the stamp objects AND without ANY non-black color artifacts remaining after changing the selection to 100% black.

Question: have you tried scanning with a dark-as-possible background* and then doing 'Colors-Levels' and dragging the right-hand slider over until the background is "solid black"?

Also, the "halo" may be a result of the height of the objects/stamps - have you tried adding weight on top of the objects to get them as flat as possible?

Chris

* something black, with a non-reflective surface.

Jay Smith
2012-01-17 20:52:02 UTC (over 2 years ago)

Seeking better "green screen" method

On 01/17/2012 03:29 PM, Chris Mohler wrote:

On Tue, Jan 17, 2012 at 2:17 PM, Jay Smith wrote:

Goal:

To be able to select the background (for change to 100% black) without any "leakage" of the selection onto the stamp objects AND without ANY non-black color artifacts remaining after changing the selection to 100% black.

Question: have you tried scanning with a dark-as-possible background* and then doing 'Colors-Levels' and dragging the right-hand slider over until the background is "solid black"?

Yes to "dark as possible" (and not shiny)

No to "Colors-Levels....". The problem in that operation is that it would also affect the related black areas in the postmarks on the stamp. The color of the postmarks should not be darkened as it would change the appearance of the image (which are actual items that people are expecting to appear in the image as they are in real life).

Also, the "halo" may be a result of the height of the objects/stamps - have you tried adding weight on top of the objects to get them as flat as possible?

I agree that height/thickness is part of the problem. Yes, we have added weight with no affect on most items.

Please note that the "weather person standing in front of a weather map" has not only their own thickness, but a foot or two between them and the map. If the room lighting is not 100% right, one can see a bit of "green screen shadow", but 99% of the time there is no shadow and no halo. I am hoping that level of success can be achieved in what I am trying to do.

Thank you Chris.

Jay

Chris

* something black, with a non-reflective surface.

Liam R E Quin
2012-01-17 20:53:01 UTC (over 2 years ago)

Seeking better "green screen" method

On Tue, 2012-01-17 at 15:17 -0500, Jay Smith wrote:

We have tried scanning on many different non-black background colors and surfaces, but there are always some extreme-edge color artifacts remaining ... leaving a sort of "halo" effect around the stamp object.

I've found that scanning object once and then rotating the object on the scanner by 180 degrees and scanning again, and combining the image, can help with that sort of object-depth effect. I've used it to get rid of (or reduce) embossed lettering on old engravings for www.fromoldbooks.org for example (also with an Epson scanner).

The reason it happens is that the scanner sensor and light have to be at an angle to avoid reflections (including from the glass!). Television cameras don't have this problem.

Liam

Liam R E Quin
2012-01-17 20:54:30 UTC (over 2 years ago)

Seeking better "green screen" method

[resending from the right account, sorry!]

On Tue, 2012-01-17 at 15:17 -0500, Jay Smith wrote:

We have tried scanning on many different non-black background colors and surfaces, but there are always some extreme-edge color artifacts remaining ... leaving a sort of "halo" effect around the stamp object.

I've found that scanning object once and then rotating the object on the scanner by 180 degrees and scanning again, and combining the image, can help with that sort of object-depth effect. I've used it to get rid of (or reduce) embossed lettering on old engravings for www.fromoldbooks.org for example (also with an Epson scanner).

The reason it happens is that the scanner sensor and light have to be at an angle to avoid reflections (including from the glass!). Television cameras don't have this problem.

Liam

Seth Burgess
2012-01-17 21:01:57 UTC (over 2 years ago)

Seeking better "green screen" method

You can try "Color to Alpha" using a background color not found on the stamp, but you may end up needing to do back-filling under the stamp (draw on a layer underneath it) where it removed a portion, and it probably won't work that well for real-world images (slight variations aren't handled well by the algorithm). You can also use a painting mode of Color to Alpha to only clean up artifacts a select-by-color and removal leaves, but that's more work.

The foreground extraction method is intended to do something similar to what you're wanting, but until the new one is ready (see http://www.youtube.com/watch?v=kkQ1r5g49d4) its only a binary selection so you'll not get nice removal of color components and you'll see bleed.

You might take a look at the Bluebox plug-in with GAP (you'll have to locate/install the GAP plugins for your platform); haven't used it personally but it seems like it has the right options.

Best of luck,

Seth Burgess

On Tue, Jan 17, 2012 at 2:29 PM, Chris Mohler wrote:

On Tue, Jan 17, 2012 at 2:17 PM, Jay Smith wrote:

Goal:

To be able to select the background (for change to 100% black) without

any

"leakage" of the selection onto the stamp objects AND without ANY

non-black

color artifacts remaining after changing the selection to 100% black.

Question: have you tried scanning with a dark-as-possible background* and then doing 'Colors-Levels' and dragging the right-hand slider over until the background is "solid black"?

Also, the "halo" may be a result of the height of the objects/stamps - have you tried adding weight on top of the objects to get them as flat as possible?

Chris

* something black, with a non-reflective surface. _______________________________________________ gimp-user-list mailing list
gimp-user-list@gnome.org
http://mail.gnome.org/mailman/listinfo/gimp-user-list

Chris Mohler
2012-01-17 21:05:43 UTC (over 2 years ago)

Seeking better "green screen" method

On Tue, Jan 17, 2012 at 2:52 PM, Jay Smith wrote:

No to "Colors-Levels....".  The problem in that operation is that it would also affect the related black areas in the postmarks on the stamp.  The color of the postmarks should not be darkened as it would change the appearance of the image (which are actual items that people are expecting to appear in the image as they are in real life).

OK - just thought I'd throw a "quick and dirty" approach out there ;)

I agree that height/thickness is part of the problem.  Yes, we have added weight with no affect on most items.

Please note that the "weather person standing in front of a weather map" has not only their own thickness, but a foot or two between them and the map.  If the room lighting is not 100% right, one can see a bit of "green screen shadow", but 99% of the time there is no shadow and no halo.  I am hoping that level of success can be achieved in what I am trying to do.

Ah, but camera != flatbed scanner.

If I was going to do an index replacement (aka "green screen"), I'd use a solid background of intense color that won't be present in the item. Then I might:

Select the background (with fuzzy select), fill with black. With the selection still active, feather it (to the approx width of the "halo" and then Colors->Desaturate.

But it's hard to come up with a workflow without seeing an example. Can you post an example scan with a colored background and "halo"?

Chris

Willie B Bass
2012-01-17 21:06:58 UTC (over 2 years ago)

Seeking better "green screen" method

Stop emailing me

Patrick Shanahan
2012-01-17 21:42:21 UTC (over 2 years ago)

Seeking better "green screen" method

* Willie B Bass [01-17-12 16:08]:

Stop emailing me
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Steve Kinney
2012-01-17 23:47:29 UTC (over 2 years ago)

Seeking better "green screen" method

On 01/17/2012 03:17 PM, Jay Smith wrote:

Problem:

The stamps are currently scanned on a black background (for lack of other color possibilities; the final goal is on a black background). After scanning, the background is selected and turned to 100% black to have greatest contrast for the object. When a stamp has a postmark that crosses the edge of the stamp paper, the color of the postmark (usually dark or black) is very close to the color of the scanning background and thus when the background is selected, the selection "leaks" and "follows" the postmark onto the stamp. We have to manually exclude those "leaks" from the desired selection area.

Hey Jay,

The first thing I would try is obtaining a set of backgrounds with strongly saturated colors, like colored construction paper, to select background colors that are not present at the edge of the stamps themselves. Then I would turn on the Fuzzy Select a.k.a. "magic want" tool to select the background area by color - with the Tool Option tab open in the dock. Adjusting the Fuzzy Select tool's threshold (way up) might get you where you want to be in selecting the background, and all of it, so that when you fill the selection you will get all of the background with no "halo effect" or unacceptable degradation of the edge of the stamp itself.

:o)

Steve

Rob Antonishen
2012-01-18 00:28:00 UTC (over 2 years ago)

Seeking better "green screen" method

On Tue, Jan 17, 2012 at 3:17 PM, Jay Smith wrote:

Is there something like that which can be used to remove a color "halo" that results from using a "green screen" approach to scanning? (I would likely have to select different colors of "green screen" so that such colors are not included in the design of the postage stamp.

If your background is fairly even, and the colours are different in the stamp, then I had written a script that might work (not having seen a sample image): http://gimpscripts.com/2011/10/transparent-background/

This will turn the background transparent by matching with the upper left colour of the background, selecting with a tolerance expanding the selection, and doing a colour to alpha as suggested by others.

Give the script a try, ir might have reasonable results. It works well for me on solid background colours.

-Rob A>

Judah Kleinveldt
2012-01-18 07:25:32 UTC (over 2 years ago)

Seeking better "green screen" method

Hi

Have tried deep-edging the image using the path tool.

I find that using that tool works best when removing a backround in an image. It takes a few minutes, though if you have many stamp-scans with the same dimensiona nd edges that single path you spent an hour creating becomes a joy to use because once you have saved that path you can load and reuse it.

Here how to do it..... docs.gimp.org/en/gimp-using-paths.html docs.gimp.org/en/gimp-path-dialog.html And lastly if you feel you familiar with all that you can visit: gimp.org/tutorials/Drawing_Shapes/

I hope this can be helpful to your work.

:) Judah