Adobe PHOTOSHOP ELEMENTS Manual page 57

About resampling
Resampling refers to changing the pixel dimen-
sions (and therefore display size) of an image.
When you downsample (or decrease the number of
pixels), information is deleted from the image.
When you resample up (or increase the number of
pixels), new pixels are added based on color values
of existing pixels.
A
B
A. Downsampled B. Original C. Resampled up
(Selected pixels displayed for each image.)
Keep in mind that resampling can result in poorer
image quality. For example, when you resample an
image to larger pixel dimensions, the image will
lose some detail and sharpness. Applying the
Unsharp Mask filter to a resampled image can help
refocus the image's details. (See "Sharpening
images" on page 98.)
To avoid the need for resampling, scan or create
the image at a high resolution. If you want to
preview the effects of changing pixel dimensions
on-screen or print proofs at different resolutions,
resample a duplicate of your file.
About interpolation methods
When an image is resampled, an interpolation
method is used to assign color values to any new
pixels it creates, based on the color values of
existing pixels in the image. The more sophisti-
cated the method, the more quality and detail
from the original image are preserved.
Photoshop Elements provides three interpolation
methods:
• Nearest Neighbor is the fastest but least precise
method. This method is recommended for use
with illustrations containing non-anti-aliased
edges, to preserve hard edges and produce a
smaller file. However, this method can result in
jagged effects, which become apparent when
C
distorting or scaling an image or performing
multiple manipulations on a selection.
Bilinear is the medium-quality method.
•
Bicubic is the slowest but most precise method,
•
resulting in the smoothest tonal gradations.
Changing the pixel dimensions of an
image
When preparing images for online distribution,
it's useful to specify image size in terms of the pixel
dimensions. Keep in mind that changing pixel
dimensions affects not only the size of an image
on-screen but also its image quality and its printed
characteristics—either its printed dimensions or
its image resolution. (See "About image size and
resolution" on page 46.)
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