The concept of a mask is simple.
Masks protect the part of the image they cover and select the part that
is uncovered. PHOTO-PAINT uses the term "mask" to describe both
the selected area and the resulting mask created by the selection.
(In Photoshop, the part selected is called a "selection," and
the image (mask) produced is called a "mask.") |
| mask marquee indicates the mask boundary |
the white areas of the mask are selected but not protected |
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above: the leaf in the photograph (left) has been selected as indicated
by the marquee surrounding it;
the actual mask created by the selection is the black portion (right)
Black, White and Gray
A mask is actually a separate image that covers the image you are working
on.
A photograph and its mask are shown above.
The original photograph (left) shows a leaf against a coloured background.
The leaf is masked, as indicated by the marquee surrounding it.
The image shown at the right is what the mask looks like:
the parts of the image covered by 100 percent black (opaque) are protected,
while any part of the image under the 100 percent white (transparent) is
not. |
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The above image looks like a black-and-white (line art) image, but it's
not: the mask is actually a grayscale image.
If the pixels in the mask can have transparency, it means that these transparent
pixels will only partially protect areas of an image.
The right image shows the mask we saw in left image after it has been feathered.
Having the opacity of a mask gradually increase as it approaches the edge
produces blurred edges of semitransparent pixels.
A blurred edge allows effects to blend into the protected areas of the image:
smooth transitions in an image fool the eye of the viewer.
Displaying
Masks
Corel PHOTO-PAINT provides a large selection of both mask-creation and mask-selection
tools. All these tools do basically the same thing: create masks.
Although a mask lies on top of an image, it is normally not visible to the
user.
Invisible things are difficult to work with: therefore, the Programmers
put several features in the program to display them. |
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The Marquee de Mask
The primary way to display a mask is the marquee: when this feature is enabled,
selecting an area with a mask produces a visual display of the mask boundary
called a marquee.
The marquee appears as a moving pattern of dash marks that is commonly referred
to as "marching ants."
Because all those moving dashes can, at times, be more of a distraction
than a help, PHOTO-PAINT allows the display to be toggled on or off by use
of CTRL-H or the Mask Marquee icon in the standard toolbar or through the
menus: Mask/Marquee Visible.
Show Mask Marquee button is part of the Mask/Object toolbar.
Two sets of tools are used when working on masks: mask creation tools and
mask manipulation tools.
The mask tools in the Mask/Object toolbar are used to manipulate the mask,
whereas the first four buttons on the left and the last one on the right
of the toolbar involve operations with objects.
The marquee shows where edges of the mask are.
Mask Overlay, which is toggled on and off from the Mask
menu, places a tint over the image that shows the actual mask.
The next illustrations show the mask overlay on (right: feathered mask applied). |
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In real life, enabling the Mask Overlay feature temporarily turns off
the marquee.
Marquees provide a quick visual indication of the status of a mask.
Mask overlay does not in any way affect the image, only the display of the
image.
If you don't like the default color, you can change the overlay color in
the same way we changed the marquee color (CTRL-J and Display). |
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Mask Creation Tool
These eight tools can be selected from the Mask Tools flyout in the Toolbox
or by pressing the shortcut key.
The mask creation tools follow:
Rectangle mask tool (R)
Circle mask tool (J)
Freehand mask tool (K)
Lasso mask tool (A)
Magnetic mask tool (before version 11:Scissors) (4)
Magic Wand mask tool (W)
Mask Brush tool (B)
Mask Transform tool (M)
Path (Node Edit) tool (. period)(version 11: among object tools)
There are two types of mask creation tools:
those used to create regular masks: the regular mask tools-Rectangle,
Circle and Freehand-create masks defined by the user; their size, shape,
and location within the image are controlled by use of the mouse or other
pointing device;
those that are referred to as the color-sensitive mask tools: this
is unlike the color-sensitive masks whose boundaries are determined by PHOTO-PAINT
from information you enter about the color values of the image; you tell
the program what color or shade you are interested in and it will look through
the entire image to find every pixel that matches the color or range of
colors you asked for. PHOTO-PAINT then creates a mask based on that information.
Color-sensitive mask tools are the Lasso, Magnetic, and Magic Wand.
After a mask is made, we can use any mask creation tool, including the Mask
Transform tool, to edit the mask.
(note:the default shortcut key
for each tool is shown in parentheses after the tool name) |
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Regular Mask Tools
These three tools create masks when you click and drag a cursor on the image.
The Rectangle Mask Tool (R)
The Rectangle mask tool is used for making square and rectangle shaped masks.
To create a mask, you only need to select the tool, click and hold down
the mouse button and drag until it has the size and shape you want.
Two keys are used as mask tool modifiers:
CTRL and SHIFT. The action produced by pressing a modifier key depends on
whether the modifier key is enabled before or after clicking the mouse button.
If a modifier key is held down before the mouse button is clicked, it will
temporarily enable the mask mode as long as it is held (Mask modes are
discussed later).
The keys only work as mask tool modifiers when held down after the mouse
button is clicked.
If you hold down CTRL after clicking the mouse button, the shape of the
mask is constrained to a square (see below).
The modifier key can be used both as a mask mode control and as a constrain
key:
hold down CTRL, click the mouse button, release CTRL, and then hold it down
again.
Holding down SHIFT produces a mask that expands outward from the starting
point, while holding down both CTRL and SHIFT creates a square mask that
expands outward from the center, as shown next. |
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The Circle Mask Tool (J)
The Circle mask tool is used to create elliptical or circular masks.
This mask tool works just like the Rectangle mask tool, except that holding
down CTRL after the mouse button is clicked constrains the mask to a circle.
This is one of the most useful masking tools for defining an irregular shape.
Almost any curved edge can be selected by changing the mask mode to Additive
mode and creating the edge of the curved edge with multiple overlapping
elliptical shapes (see below).
The Freehand Mask Tool (K)
The Freehand mask tool is really two tools in one.
As long as the mouse or stylus button is held down, the mask tool is in
Drawing mode and acts much as a pencil or pen would.
The mask boundary is created as you draw an outline surrounding the area
you want to edit. When the pointing device button is released, the Freehand
mask tool reverts to Polygon mode. In this mode, you need only click at
different points in your image to define the boundaries; between each click,
PHOTO-PAINT creates a straight line.
When you have finished with your mask, either double-click the last point
or hold down ALT and click the mouse/stylus button to complete the mask. |
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To illustrate how the Polygon mode of the Freehand tool works, look at
the example above (right).
The mask begins by clicking at point with red circle.
As the cursor is moved to point 2 on the example, a continually updated
display of the mask shape is shown.
Each time the cursor is clicked, a new point of the mask boundary is created.
Clicking DEL removes the last point.
Clicking at points 3-6 produces the shape shown in the preceding illustration.
The cursor still appears untill the mask has not been completed.
A straight line is continuously displayed between the current cursor position
and the starting point.
Freehand Mask Tool Modifier Keys
Just like the other mask tools, the Freehand mask tool has modifier keys.
Holding down CTRL and the mouse button in Drawing mode constrains the mask
cursor movement to horizontal or vertical strokes.
To change the direction of the constraint, use CTRL-SHIFT.
In Polygon mode, CTRL constrains creation of strokes to 45-degree angles.
DEL is used in either mode to remove the last point on the mask.
Each time DEL is pressed, another point is removed; this "undoing"
of the mask can continue all the way back to the starting point.
When clicking at multiple mask boundary points in Polygon mode, ensure you
don't click the button too fast, or else PHOTO-PAINT will misinterpret it
as a double-click and complete the mask.
Corel's dualistic approach to the Freehand mask tool offers two advantages
over the traditional freehand tool.
Traditionally, a freehand-type tool is difficult to use because the mouse,
being a relative motion device, does not have the control necessary to accurately
trace a complex line.
The other limitation of the Freehand mask tool becomes apparent the first
time you release the mouse button: traditionally, a freehand mask is completed
with a straight line back to the starting point as soon as the button is
released, that is, when you begin to make a mask, you cannot release the
button until the mask is finished.
In PHOTO-PAINT, the Freehand mask tool simply changes mode when the mouse
button is released, allowing you to rest when creating a lengthy and detailed
mask.
Combining the Drawing mode and the Polygon mode makes it possible to use
a mouse to mask irregularly shaped objects with some degree of accuracy.
For irregular mask creation with a mouse, I recommend using the Polygon
mode of the Freehand mask tool and changing the shape of the tool cursor
to a Crosshair when using the Freehand tool to trace complex shapes: it
is much easier to see and, thereby, follow an edge with this cursor.
(note: to change the cursor shape, open Preferences (CTRL-J) and from
the General setting, set the Cursor Type to Crosshair) |
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Mask Modes
The mask tools do not retain individual mask mode settings: for example,
if you are using the Rectangle mask tool and the XOR mode is selected, any
other mask tool you select will also be in XOR mode.
Normal
Mask Mode
In Normal mask mode, masks are mutually exclusive: that is, making a mask
deletes any existing mask in an image.
If a mask doesn't look right, just make another one.
The purpose of the other mask modes is to allow us to add to, subtract from
and otherwise modify any existing mask:
Normal: every time
you make a mask, any existing mask is removed (ALT-NUMPAD .
(period)); Additive: each mask tool action adds to the
existing mask (ALT-NUMPAD +);
Subtractive:
each mask tool action subtracts from the existing mask (ALT-NUMPAD -);
Exclusive OR (XOR): if the portion of the new mask being added
overlaps an existing mask, the mask properties of the overlapped area are
inverted (ALT-NUMPAD *).
Mask modes can be selected from the Mask menu, through keyboard shortcuts
or through toolbar buttons.
The mode of the currently selected mask tool is indicated by an icon displayed
in the status bar and by the shape of the cursor.
Additive and Subtractive
Mask Modes
Additive mode: each time you use a mask tool, you add to the previous mask.
Subtractive mode: any mask tool actions taken remove the portions from the
selected area.
XOR Mask Mode
With XOR mask mode enabled, if you
Create a mask on an image that doesn't have a mask, the mask will act normally;
Add a second portion to the mask that doesn't overlap the first mask, it
will act like Additive mode;
Add a second portion that falls entirely within the existing mask, it acts
like Subtractive mode; Add a mask that overlaps a portion of an existing
mask, the portion of the image already selected by a mask covered by the
XOR mask will be inverted. |
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This, above: it is a good time to ensure that you understand an important
concept in masks. Here is a little test (have enabled the grid and used
the Circle mask tool to create the circles indicated by the mask marquee):
How many masks do you see?
The correct answer is one mask composed of seven selected areas.
The actual mask is shown at the right of the image. |
| color sensitive mask, isolate the shadows in the original (a) |
and apply correction to recover detail in the shadows (b) |
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Color-Sensitive Masks
This category of tools allows you to create incredibly complex masks quickly.
The color-sensitive mask tools are Lasso, Magic Wand,
Magnetic (ex Scissors) and Color Mask. The Color mask tool
is the only mask tool not located on the mask flyout (it is accessed
through the Mask menu).
The photograph, above, is an example of a photograph that needs to have
the shadow areas lightened without making the lighter areas any lighter.
By using the Color mask we have been able to isolate the shadow portion
of the photograph from the light areas and using Tone curve we have recovered
the detail in the shadow area and have a much more balanced photograph,
as shown in right photo (with a different editing in the other areas).
The success of the three color-sensitive mask tools discussed here depends
on the Color Similarity setting the user applies in the property bar.
The higher the value, the greater the number of colors that will be included
in the resulting mask.
The key to finding the optimum tolerance level is experimentation.
There are two modes: Normal and HSB.
Normal method bases its
selection strictly on the color similarity of adjacent pixels;
HSB
method lets you fine-tune the selection according to the similarity of a
combination of hue, saturation, and brightness levels between adjacent pixels. |
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The Lasso Mask Tool (A)
 The Lasso mask tool is used to create an irregular mask based on an image's
color values and the Tolerance level.
When you click the starting point of the mask, PHOTO-PAINT samples the color
value of the pixels under the starting point.
A mask is created in the same manner as with the Freehand mask tool.
Once you have surrounded the subject you want selected with the Lasso mask
tool, double-click the mouse button and the marquee shrinks until it surrounds
an area with color values that fall within the limits set by the Color Similarity
slider in the property bar. |
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The Magnetic Mask Tool (4)
(vers 11, Scissors vers 10)
The Lasso mask tool is great when you have a background with very similar
colors.
When the background contains many different colors, you can use the Scissors
mask tool, which automatically detects edges in your image and places the
mask marquee along those edges as you are outlining the mask.
The Scissors mask tool uses Color Similarity values in the property bar
within the area of the tool's bounding box.
When you select this mask tool, an invisible bounding box surrounds the
Mask Tool cursor and remains centered at each successive point on the mask.
The Scissors mask tool doesn't look at the color content of the entire image;
it only looks at the area inside the bounding box.
The first click is placed near the edge of the subject you want to select.
This first point establishes the color sample used for Color Similarity
comparisons.
The Scissors mask tool evaluates all of the pixels within the 200 x 200
pixel bounding box to determine where to place the edge.
As you move the cursor along the edge you want to select, a line appears
indicating where the mask will be placed.
Every time you click the cursor along the edge, it creates a new center
for the bounding box. When using this tool, here are some rules to make
it work better:
if the area you want to select contains a lot of similar colors, you need
only click the tool at a few points and the tool won't have any trouble
detecting the edge;
if the background contains many different colors, you need to reset the
center of the bounding box more often: this is because as you approach or
go beyond the edge of the current bounding box, the tool has greater difficulty
detecting the edge.
One problem is when the color/shades that define the edge between the foreground
and the background are too close: when this happens, either click many points
close together or click and drag the mouse like a Freehand mask tool
(this technique works best when used with a stylus instead of a mouse). |
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The Magic Wand Mask Tool (w)
The Magic Wand mask tool is the converse of the Lasso mask tool.
It creates masks by expanding from a starting point until all the adjacent
colors meeting the selection criteria are included.
As with the other color-sensitive mask tools, the ability of the Magic Wand
to make an accurate mask depends on the Color Similarity settings in the
property bar and the actual color-value composition of the image.
The Magic Wand tool is very simple to use once you understand the concept
behind its operation.
In theory, you simply click the area that needs to be masked and PHOTO-PAINT
reads the color value of the starting pixel and, using the Color Sensitivity
level, expands the mask selection pixel by pixel until it can no longer
find pixels that are within the limits.
For example, if the starting pixel has a value of 60 and the Color Sensitivity
value has been set to 50, the mask will expand from its starting point until
every adjacent pixel with a value between 10 (60 minus 50) and 110 (60 plus
50) has been included in the mask.
When you 're using the Magic Wand mask tool, the most important decision
to make is the choice of whether to mask the object or the area around the
object.
If the area to be protected is filled with a wide variety of colors or colors
with a wide tonal range, then look at the area surrounding it: remember
that it only takes one click of the button to invert a mask.
The
Grow and Similar Commands
These two commands increase the size of an area selected by a mask.
Both commands determine which pixels are included in the mask according
to the current tolerance setting of the Magic Wand mask tool.
Grow
With an existing mask on the image, choose Mask/Shape/Grow to include all
pixels that neighbor the existing mask and those that fall within the range
of colors included in the mask.
All the pixels eligible for selection by Grow must be contiguous (adjacent
to one another).
The color range of pixels selected is determined by the Color Similarity
setting.
If you need to change the setting, it is first necessary to select the Magic
Wand mask tool. Similar
With an existing mask on the image, choose Mask/Shape/Similar.
The Similar command acts like the Grow command, except that the eligible
pixels do not need to be adjacent to one another.
As long as the pixel's color value falls within the color range specified
by the Color Similarity setting, it will be included regardless of where
it is in the image.
Color Similarity and Magic Wands
The Color Similarity is critical to getting satisfactory results with the
Grow and Similar commands when used in conjunction with the Magic Wand.
When you apply the Magic Wand using a relatively high setting (>30),
applying the Grow command without changing the Color Similarity value will
result in a blown mask, that is, a mask that overruns most color boundaries:
this happens because of the cumulative effect of applying the Magic Wand
with a setting of 30 percent on top of a 30 percent Grow setting.
The best way to use it is either to use low values for both selections or
to use as high a setting as necessary for the Magic Wand to do its job and
then decrease the setting of the Grow command.
Properties of
Mask and Selection
If you move an existing mask using a mask tool in Normal mode (except the
Mask Brush or Mask |
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Transform tool), it becomes a selection:
if ALT is held down when the selection is created, the original image in
the masked area remains; if not, it is replaced with the current Paper color
if it is a flat image with no objects; a selection can be moved around an
image, even beyond the edge of the image borders and it will still maintain
both its shape and its contents;
if a selection is dragged completely off the image, it becomes a new image.
The Mask Transform Tool (M)
The Mask Transform tool is found on the flyout with the Object Picker tool.
The Mask Transform tool is actually a mask modifier.
All masks created with the mask tools can be moved, scaled, rotated, skewed
or have perspective applied.
When the Mask Transform tool is selected, eight handles appear on the existing
mask.
Clicking inside the mask changes the shape of the handles, indicating the
transform mode.
The transform mode also appears in the property bar.
There are many ways to manipulate a mask using this tool, but you will find
its most commonly used function is to move a mask on an image or to change
the size (scale) of a mask.
The other transform functions are mostly used when working with objects.
Whenever you apply a transformation to a mask, be sure to double-click the
mask to complete the transform action.
Until you complete the action, most of the PHOTO-PAINT commands will be
unavailable. |
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The Mask Brush Tool (B)
The Mask Brush tool is used to modify both the regular and the color-sensitive
masks.
 This is the ultimate mask clean-up and touch-up tool.
The Mask Brush tool enables you to brush or paint an area to be masked.
Unlike a regular brush tool that applies color to an image, the Mask Brush
tool can be used to apply or remove a portion of a mask using the Additive
and Subtractive modes.
The size and shape of the Mask Brush tool are set from the property bar. |
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