"perfect" cut outs?

Google for Ultimatte and Primatte

For moving pics (video) you really need After Effects with a Matte / Keyer plugin.

There are also many hardware solutions for matte / key / composite work.

Guy

"bugbear" wrote in message

In films it is now routine to shoot against
blue (or green) backgrounds, and get absolutely perfect
cut-out masks, such that the cut
out character can be merged into a new background
(with no "blur", "edge" or other artefacts), over 100’s of film frames.

These technique
appear to be fully automated, and not involve
selecting, drawing, "magic wands" etc.

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

BugBear

Do a google seach fore "Chromakey Photoshop" and a bunch of stuff comes up, including this link that explains it pretty well.

http://www.seanet.com/~bradford/bluscrn.html

The other place you see it every day, nearly flawlessly, is the weather forecast. Watch the weather guy, he isn’t looking at the map, he is looking to the side of the map so that he can see himself in front of the map. He also generally has a monitor in front of him so see himself in front of the map. Here, you have the technique being done live. It is also why he doesn’t wear a blue shirt or tie.

Bigguy wrote:

Google for Ultimatte and Primatte

Ouch. After googling, I’ll need to pull some
overtime 🙂

I can’t find any "magic" sequences that one
could do in PhotoShop or Gimp etc.

But there are some good algorithms
"coming down the pike"

http://grail.cs.washington.edu/projects/digital-matting/ "bayesian matting" shows better results
than ultimatte (in some contexts)

A Bayesian Approach to Digital Matting (2001)
http://citeseer.ist.psu.edu/chuang01bayesian.html

And this has been followed up by:
Trimap Segmentation for Fast and User-Friendly Alpha Matting http://citeseer.ist.psu.edu/731634.html

and something called siox is heading for the Gimp.
http://www.siox.org/

BugBear

On 1 Feb 2006 07:06:46 -0800, in rec.photo.digital , "Pat" in
wrote:

Do a google seach fore "Chromakey Photoshop" and a bunch of stuff comes up, including this link that explains it pretty well.

http://www.seanet.com/~bradford/bluscrn.html

The other place you see it every day, nearly flawlessly, is the weather forecast. Watch the weather guy, he isn’t looking at the map, he is looking to the side of the map so that he can see himself in front of the map. He also generally has a monitor in front of him so see himself in front of the map. Here, you have the technique being done live. It is also why he doesn’t wear a blue shirt or tie.

It is an interesting use of technology to replicate a low tech solution. The better question is why do we need to see the weatherman at all? That blocks the map, just show the map and a pointer. That does it all in the computer much cheaper. But people like to see the person.

—
Matt Silberstein

Do something today about the Darfur Genocide

http://www.beawitness.org
http://www.darfurgenocide.org
http://www.savedarfur.org

"Darfur: A Genocide We can Stop"

bugbear wrote:

In films it is now routine to shoot against
blue (or green) backgrounds, and get absolutely perfect
cut-out masks, such that the cut
out character can be merged into a new background
(with no "blur", "edge" or other artefacts), over 100’s of film frames.

These technique
appear to be fully automated, and not involve
selecting, drawing, "magic wands" etc.

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

—–
Chroma-key or green screen? Select the background color using your preferred method of choice and delete.

Create a New Layer and paste in your background of choice.

In film it’s sometimes referred to as A-B roll, mixing 2 sources (roll A & roll B) to create a composite image using the control or editing board.

There’s also Lumi-key, less precise but doing the same thing based on the luminence of the original image.
—–

– gpsman

"bugbear" wrote in message

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

Photoshop has a background eraser too that can do a reasonable job if your (preferably monochrome) background is well saturated and evenly lit, and you’re prepared to be patient experimenting with the best tolerance.

C J Southern wrote:

"bugbear" wrote in message

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

Photoshop has a background eraser too that can do a reasonable job if your (preferably monochrome) background is well saturated and evenly lit, and you’re prepared to be patient experimenting with the best tolerance.

In other words, it doesn’t work that well. I often wondered why Paint Shop Pro’s background eraser works so much better that Photoshops … I’m still wondering.

"Steve" wrote in message

Photoshop has a background eraser too that can do a reasonable job if

your

(preferably monochrome) background is well saturated and evenly lit, and you’re prepared to be patient experimenting with the best tolerance.

In other words, it doesn’t work that well.

It’s proportional to the saturation of the chromakey and the evenness of the lighting.

I often wondered why Paint
Shop Pro’s background eraser works so much better that Photoshops … I’m still wondering.

Can’t help you there – I’ve never used PSP.

C J Southern wrote:

"bugbear" wrote in message

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

Photoshop has a background eraser too that can do a reasonable job if your (preferably monochrome) background is well saturated and evenly lit, and you’re prepared to be patient experimenting with the best tolerance.

Corel KnockOut 2. I haven’t used it but a friend who does a lot of background removal for artistic photos used the original Knockout (pre Corel) and swore by it.

Chip Gallo
www.flickr.com/photos/chipgallo

In article <43e0a406$0$6993$>,
bugbear wrote:

In films it is now routine to shoot against
blue (or green) backgrounds, and get absolutely perfect
cut-out masks, such that the cut
out character can be merged into a new background
(with no "blur", "edge" or other artefacts), over 100’s of film frames.

These technique
appear to be fully automated, and not involve
selecting, drawing, "magic wands" etc.

Does anyone know enough about these techniques
to apply them to a simple, single still image,
using standard desktop apps (Gimp, Photoshop,
ImageMagick etc).

Provided the thing you want to cutout is sharply focused, or has good contrast with the background, the magnetic lasso will work. You simply tidy up the few errors with an ordinary lasso adding or subtracting from the selection. Feathering is necessary but only with a few pixels otherwise you’ll end up with a halo. This can be minimized with a very soft eraser with the opacity down to 30%. Hair (and other complicated outlines) is one of the biggest problems, but the clone tool or smudge tool can help here. Quick mask mode should give a clear indication of what you can expect.