Computer Graphics with Photoshop - Selecting complex objects

Author

Selecting complex objects

als_trash@hotmail.com

2006-07-10, 6:18 pm

Hi All,

I'm trying to select just the leaf in the following picture:
http://grove.ufl.edu/~ashenkin/1-2-19.jpg

I've tried using magic wand in various steps, and it gets pretty good
if I work at it for a while using channels. The problem is that I have
about 120 of these images to process and would prefer to find a better
way to do it. I've downloaded Mask Pro 3, and that doesn't seem to do
as well as just using the magic wand when I set up keep and drop color
pallets.

I'm thinking of this problem in 2 ways: one part of it is selecting
based on color. The problem is that, between the leaflets, the color
of the white background gets shaded and looks rather like the color in
some of the leaflets. So the second part I would like to incorporate
is a sense of edge in the image, rather than pure raster colors. It
seems to me this should be a doable task, but I'm not sure if the tools
are available to accomplish it.

Thanks for any thoughts!

Best,
Allie

Hebee Jeebes

2006-07-10, 6:18 pm

I would go with quick mask mode, zoomed in a good amount and a small hard
edged brush. Most masking plug-ins just don't cut it.

R

als_trash@hotmail.com

2006-07-10, 6:18 pm

Thanks R. The problem with that approach is that it would suck up tons
of time. As I mentioned, I've done pretty well with the magic wand,
which is quicker than a quickmask, but still looking to get a bit
quicker and sophisticated, if possible. Thanks again.

Mike

2006-07-10, 6:18 pm

<als_trash@hotmail.com> wrote in message
news:1150484688.953493.263290@u72g2000cwu.googlegroups.com...
> Hi All,
>
> I'm trying to select just the leaf in the following picture:
> http://grove.ufl.edu/~ashenkin/1-2-19.jpg
>
> I've tried using magic wand in various steps, and it gets pretty good
> if I work at it for a while using channels. The problem is that I have
> about 120 of these images to process and would prefer to find a better
> way to do it. I've downloaded Mask Pro 3, and that doesn't seem to do
> as well as just using the magic wand when I set up keep and drop color
> pallets.
>
> I'm thinking of this problem in 2 ways: one part of it is selecting
> based on color. The problem is that, between the leaflets, the color
> of the white background gets shaded and looks rather like the color in
> some of the leaflets. So the second part I would like to incorporate
> is a sense of edge in the image, rather than pure raster colors. It
> seems to me this should be a doable task, but I'm not sure if the tools
> are available to accomplish it.
>
> Thanks for any thoughts!
>
> Best,
> Allie
>

Go into your channels and identify the channel that has the best contrast
between the leaf and the paper (don't worry about the rest of the image.) I
guess it will be the green channel (in RGB) - I don't have Photoshop on this
computer so I can't work on it myself.

Now, duplicate the channel (using the arrowhead flyout on the Channels
pallette). Working on the duplicate channel ONLY, call up levels and adjust
the three sliders so that the leaf is perfectly seperated from its
surroundings - don't worry that you are mashing this channel to pieces, it's
only for a selection!! You can make very extreme adjustments with the three
levels sliders - the idea is to break the leaf shape away from its
surroundings.

Now, get a paintbrush and paint around the image in black and white as
necessary so that the leaf is absolutlely cut away from everything else. Go
back to your RGB composite channel, go Select-Load Selection and choose the
channel you just created. Your marching ants should show a pretty clean
selection now.

grannysdc

2006-07-10, 6:18 pm

A simple easy way of Masking out Difficult Images in Photoshop is to use
Color range then use Channels to help mask out a complex objects with
clean edges as presented in the Photoshop Tutorial by COLIN SMITH at:
http://www.photoshopcafe.com/tutori...ing/masking.htm
Granny likes simple and easy

<als_trash@hotmail.com> wrote in message
news:1150484688.953493.263290@u72g2000cwu.googlegroups.com...
> Hi All,
>
> I'm trying to select just the leaf in the following picture:
> http://grove.ufl.edu/~ashenkin/1-2-19.jpg
>

als_trash@hotmail.com

2006-07-10, 6:18 pm

Thanks Mike and Granny,

The idea of using levels is a good one.

Mike, the one issue with your method is that some of the pixels I don't
want are of similar color to those I don't want. So, adjusting the
levels doesn't quite help me all that much. Algorhitimically, these
similarly-colored pixels should be somewhat separable through edge
detection, which is what I was getting at before. Those pixels could
be dealt with, as you mention, through use of a paintbrush/pencil.
Again, we get into the issue of time-consumption.

Granny, I think Colin's algorithim amounts to the same method as
Mike's, with some good ideas of how to fill in areas which were spotty.

Thanks for both your ideas - I appreciate your input.

Best,
Allie

Hebee Jeebes

2006-07-10, 6:18 pm

Actually, not as much time as you think. Doing it with a plug-in you have to
learn the plug-in and then you have to fix the less than perfect masking
generated by the plug-in. This will take more time than Quick Mask mode and
a paint brush. Using the lasso tool or other methods and do a good job at it
will take probably more time. If you zoom to say 300 or 400 perfect the
Quick Masking goes fast. Just edge the out side with a small brush so it is
nice and tight and then use a larger brush zoomed out to fill in. Don't use
the fill tool, you will get an edge between the fill and the brushed edge.
Just paint it in. I have found very few things that I couldn't mask out this
way and quickly tool. A graphics tablet will make things faster, but a mouse
works fine too.

R

Hebee Jeebes

2006-07-10, 6:18 pm

The problem with things like Magic Wand and Lasso is that they don't came
anywhere close to doing a good job, not without a lot of extra fine tuning
work which can take more time than just using the Quick Mask mode and a
brush.

R

als_trash@hotmail.com

2006-07-10, 6:18 pm

I forgot to mention that, in the end, I'm only interested in getting
the total area of these leaves. Thanks again to all who have replied!

allie

My View

2006-07-10, 6:18 pm

Also check out Advanced Masking tutorial (movie) at Russell Brown's website
along with a couple of other masking techniques at this site.
http://www.russellbrown.com/tips_tech.html

<als_trash@hotmail.com> wrote in message
news:1150497796.555049.58800@h76g2000cwa.googlegroups.com...
>I forgot to mention that, in the end, I'm only interested in getting
> the total area of these leaves. Thanks again to all who have replied!
>
> allie
>

theartist

2006-07-10, 6:18 pm

My View wrote:
> Also check out Advanced Masking tutorial (movie) at Russell Brown's website
> along with a couple of other masking techniques at this site.
> http://www.russellbrown.com/tips_tech.html
>
>
>
> <als_trash@hotmail.com> wrote in message
> news:1150497796.555049.58800@h76g2000cwa.googlegroups.com...
>
>
>
>
I was looking all over adobe's site for this one. I think it's exactly
what als_trash needs.
Thanks for the link; I bookmarked that puppy.

--
§¦: } theartist

als_trash@hotmail.com

2006-07-10, 6:18 pm

Thanks for the tip. Good video. However, my problem remains that some
of the colors I want to mask out are the same colors that I want to
keep. Dodging and Burning aren't going to do the trick for me.
Channel Mixing doesn't differentiate the areas I need differentiated,
because the keep/drop colors, in the tight areas, are essentially the
same. The real difference between the keep areas and the drop areas
are that the keep areas are enclosed within circles of like colors,
while drop areas are between those circles (not enclosed).

In the end, I've reconciled myself to do a first cut selection with a
magic brush to get the general range of colors I'm looking for, then
using a quick mask to fine tune that selection.

I still hold to my opinion that color differentiation married with edge
detection/contour mapping algorithims should, in theory, be able to
tackle this problem. Taking a look at a high-pass filtering of the
image gives an idea of where one might start. But it's something,
apparently, yet to be developed. Thanks very much, everyone, for all
your help. This has been interesting and educational.

Best,
Allie

theartist wrote:
> My View wrote:
site[color=darkred]
> I was looking all over adobe's site for this one. I think it's exactly
> what als_trash needs.
> Thanks for the link; I bookmarked that puppy.
>=20
> --=20
> =A7=A6: } theartist

My View

2006-07-10, 6:18 pm

Any chance of adding a small jpeg of the image to your next reply so we can
see exactly what you are after.

<als_trash@hotmail.com> wrote in message
news:1150734615.371551.277430@y41g2000cwy.googlegroups.com...
Thanks for the tip. Good video. However, my problem remains that some
of the colors I want to mask out are the same colors that I want to
keep. Dodging and Burning aren't going to do the trick for me.
Channel Mixing doesn't differentiate the areas I need differentiated,
because the keep/drop colors, in the tight areas, are essentially the
same. The real difference between the keep areas and the drop areas
are that the keep areas are enclosed within circles of like colors,
while drop areas are between those circles (not enclosed).

In the end, I've reconciled myself to do a first cut selection with a
magic brush to get the general range of colors I'm looking for, then
using a quick mask to fine tune that selection.

I still hold to my opinion that color differentiation married with edge
detection/contour mapping algorithims should, in theory, be able to
tackle this problem. Taking a look at a high-pass filtering of the
image gives an idea of where one might start. But it's something,
apparently, yet to be developed. Thanks very much, everyone, for all
your help. This has been interesting and educational.

Best,
Allie

theartist wrote:
> My View wrote:
> I was looking all over adobe's site for this one. I think it's exactly
> what als_trash needs.
> Thanks for the link; I bookmarked that puppy.
>
> --
> §¦: } theartist