Simpler shapes
or themes, distinctly separating from the background, are very easy
to cut for, say, placing them into another picture or a different
backdrop. However, more complex shapes like animal fur, hair or foliage
often trick the software. Masking out a theme can be conveniently
solved by dedicated tools like the recently renewed ReMask
3 by TopazLabs.

It is a Photoshop
plugin with the primary aim of making the time-consuming
process of masking quicker and more accurate.
A 30-day trial
version is available from the developer's website at no cost, so that
you'll know what you're buying. It is unlimited in its functions,
and its trial period can be activated using a free serial. The downloadable
file is about 35MB, which is not really small for a plugin. Installation
is very easy, practically fully automatized. Open Photoshop and load
the photo from which you want to crop the shape, and click Filter/Topaz
Labs/Topaz Remask 3 to start the plugin.
This is our sample
photo, and the shape we want to cut out is of course the cat.

The task won't
be very easy. Although the main theme has quite different colors,
the picture rather lacks sharpness in original size, and the pet's
contours are not very defined everywhere.

Topaz
ReMask
is a pretty complex software, so at first, we'll only cover the basics—how
to crop what you want, in the least time.
This
is how the plugin's user interface looks. In the preview area, a green
veil covers the image. This green veil represents areas to be preserved.
This means, for now, the whole picture is selected. However, we only
want the cat, so that is the only part which should remain green.
The
most important masking tools the plugin offers are on the toolbar
in the upper left part (Brushes - Basic). There are
buttons with a green, a red and
a blue brush.
Use
the green one to paint over parts you want to retain. The red one
is for masking out the areas you want to get rid of— it is a marker
for unwanted elements. The blue one can be used to mark the working
area for the cropping software—that is, the contour along which you
want to crop the theme.

In the
first step of masking, click the blue brush. The Brush Size
slider can be found a little below. You can use any size. The point
is to have a conveniently thick brush as you don't need to be very
accurate with the marking.
Before
starting the selection, you may want to set zooming to the original
size. Under the preview image in the upper left corner, click the
1:1 button. Hold down Shift and
drag the mouse pointer to pan the picture.
Now
carefully draw a contour with the blue brush around the theme to be
cropped so that one half of the blue line covers unnecessary background
and the other the edge of the theme.

Work your way with
this method around the whole area to be cropped. You don't need to
be totally accurate, since it is the software that will calculate
the exact place of the cropping (the mask borders). This is a very
quick procedure, even a more complex, hairy, bushy, furry shape can
be marked around roughly in a few seconds.

The blue border
specifies where the plugin should consider the mask borders, and the
red area sets what is to be discarded by any means. You can use the
red brush to paint over the latter areas, but you'd better select
the red tool from the Fills toolbar and click anywhere
outside the blue border. But before doing so, click the Fit
button on the left of 1:1, to switch back to a smaller
zoom.

So, the
selection is done. The green areas are to be retained, the blue one
is the working area to be considered by the plugin, and the red one
is to be discarded. Click Compute in the lower left
corner to start the necessary calculations for masking out the selected
shape.
After
the computing, the plugin automatically switches to Mask
view, showing the cropped area in white, and the discarded one in
black. As you can see, the cat was not cropped exactly along the blue
area—the plugin calculated where the fur and the background meet within
the blue region.

You can
switch views using the tabs above the working area:
Image:
the original picture
Trimap: the three-color selection
Mask: mask view in black and white
Keep: the cropped, retained area
Cut: the discarded area
Here's the cropped picture. This method was way faster and a lot more
accurate than using the good old manual selection procedure. The cat
has been put on a new layer, so you can put any kind of background
behind it, or you can copy and paste it into another image.

A coming
article will discuss how to refine the edges of a calculated mask.
For instance, there are a few chamois background remains along the
cropping. Topaz ReMask can handle them, too.