What is the Bounding Box?
All digital images, including objects in Picture Publisher, are
rectangular in shape. The object can visibly have any shape; however, the object is
"bounded" or enclosed by a rectangular container. Any pixel in that object can
be assigned a transparency level of 0-255, with total opacity at 255 and complete
transparency at 0. This "transparency level" is controlled by the alpha channel.
The alpha channel exists in all image modes of Picture Publisher, including line art.
There is an exception for line art. You only control two levels in line art, on or off.
This is why you lose gradual transitions when converting images to line art. If you
convert an image from RGB or gray scale, to line art and back you will regain control of
all 256 transparency levels. To store gradual transitions in line art objects converted
from RGB (gray scale or CMYK) you MUST save the file in a Picture
Publisher native file format (.ppf, .pp5, .pp4).
Why Should You Care?
To accurately place objects with the alignment commands (including snap-to-grids) the
object's bounding box must be as small as possible. The initial bounding box of an object
created in Picture Publisher defines the exact height and width of that object. However,
actions such as transforms and alpha channel painting can severely distort the size of the
bounding box.
Just the Facts
A simple duplication of the object (Ctrl + d - or copy and paste)
will create a new object with an optimized bounding box.
The newly created object has a bounding box of minimum size.
A Detailed Tutorial
You will create a new file and object. A rotation transform will be applied to the object
inflating the bounding box. To complete the tutorial you will duplicate the
object the copy is an optimally bounded
object.
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1. Create a new file of any size and resolution |
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2. Image can be RGB, Gray Scale, CMYK, or line art. |
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3a. Create a rectangular shaped mask. |
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3b. Select the rectangle shape. Then while holding down the left mouse button create the shape shown on the left. |
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4. Convert the mask into an object (right mouse button menu). |
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5. Fill the object with the active color. |
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6. Select the transform tool to view the outside dimension of the object. The eight blocks define the perimeter of the bounding box. |
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7. Select the object and rotate 45 degrees clockwise and then 45 degrees counter clockwise. |
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8. Select the transform tool to view the perimeter of the bounding box. Note that the rotation has dramatically increased the size of the bounding box. |
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9. Duplicate the object. |
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10. The dimensions of the bounding box now reflect the visual appearance of the object. Delete the object with the oversized bounding box to complete the tutorial. |