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Section III Digital Postprocessing
is far too low for acceptable print quality (even
if you had a printer that could handle paper
nearly four feet wide!). For a file output at 300ppi,
the dimensions is much more manageable:
approximately 7″ × 10″.
Obviously, you need the ability to change
either or both of those image characteristics.
In Photoshop, use the
Image Size
dialog (other
programs have similar controls), Figure 15-10. The
dialog has three sections:
•
Pixel Dimensions
(file size and width/height
in pixels)
•
Document Size
(width/height/resolution)
•
Options
(three check boxes)
The uppermost section shows the file size in
kilobytes (K) or megabytes (M), and the width
and height dimensions in pixels. Clicking on the
down arrow at the right end of the
Width:
line
will allow you to select the value percent instead
of pixels. This is useful if you want to change
the size of the image by a specific percentage,
such as 75 (three-fourths original size) or 33
(one-third original size). Note that there is a
chain-link symbol to the right of both the pixel
dimensions and the document size sections.
This symbol indicates that the width and height
dimensions are linked so that they are changed
proportionally. If you change the width by one-
half, the height will change by one-half as well.
(This behavior is controlled by the
Constrain
Proportions
check box in the options section at
the bottom of the
Image Size
dialog. It will be
discussed later in this section.)
The middle section lists Width, Height, and
Resolution
of the image. Width and height can be
displayed in a number of different measurement
units, depending on the user’s preferences.
Clicking on the down arrow at the right will
open a drop-down menu showing the choices,
Figure 15-11. The
Resolution
drop-down lists two
choices:
pixels/inch
and pixels/cm.
At the bottom of the dialog are three
checkboxes representing options for resizing
and changing resolution. The first,
Scale
Styles,
affects only special effects applied to a file, such
as a border or a drop shadow on type. When the
box is checked, it will ensure that any effects
are scaled proportionally with changes in the
image dimensions. This box usually remains
checked.
When the
Constrain Proportions
box
is checked, any change in width will be
accompanied by a corresponding change in
height, and vice versa. This avoids any distortion
of the image when it is enlarged or reduced.
If the box is unchecked, you can stretch or
squeeze the image by changing the dimensions
independently. This capability is useful primarily
Figure 15-10. The
Image Size
dialog provides infor-
mation on the current file size, image dimensions, and
resolution. It can be used to change the resolution, the
dimensions, or both values. When the resolution and
image dimensions are altered, the file size will increase
or decrease.
Figure 15-11. A drop-down menu offers a number
of choices for measurement unit displays. Pixels,
inches, mm (millimeters) or cm (centimeters) are most
commonly used.