Selecting a Region of Color

Selecting a Region of Color

Post by Craig Austi » Fri, 05 Jul 2002 05:30:29



Could someone let me know where to find an algorithm that will find the
points along the edge of a region of color (similar to flood fill but
only return the boundary).  Paint Shop Pro does this with their "magic
wand" tool.

Thank you very much,

Craig

 
 
 

Selecting a Region of Color

Post by Hans-Bernhard Broeke » Fri, 05 Jul 2002 17:24:05



> Could someone let me know where to find an algorithm that will find the
> points along the edge of a region of color (similar to flood fill but
> only return the boundary).  Paint Shop Pro does this with their "magic
> wand" tool.

It's quite simple.  How do you mark the border of a lake if you're
started swimming in it?  You swim to shore, and take a walk around the
lake.  That's really all there is to it.  The only tricky parts are to
set up a useful definition of the "shore", and how to trace the shore,
always keeping water to your left, and land to your right.
--

Even if all the snow were burnt, ashes would remain.

 
 
 

1. How to make selected region totally transparent?

Hi all,

Using PS 5.5. I have some pics I shot with a white seemless background.

I am able to select the background portion I want to make transparent.
The selection I done by isolating the outer region with the magnetic
lazo and then using 'color range' (tunning up the fuzziness til
everything I care to select gets selected, I want to keep some of the
shadows).

The pic is indeed in a "layer" (as oposed to the "background"). So I
'cut' and *most* of it becomes transparent except for some regions,
which kinda look transparent as long as you don't go to indexed color
(ie, saving a gif). Why is this? It looks like these regions were
selected, as far as I can tell (that is, they are within the ants
borders). So why don't they get completely cut out?

Thanks.

Miguel

--
Miguel Barrio                           "Be free, love who you will,
miguelito(AT)pobox.com                   and be who you are."
http://pobox.com/~miguelito              -- Brandon Lacy

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