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                <h1>
                    Resampling
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                <div><p><dfn class="term">Resampling</dfn> is
changing the amount of image data as you change either the pixel dimensions
or the resolution of an image. When you <dfn class="term">downsample</dfn> (decrease
the number of pixels), information is deleted from the image. When
you <dfn class="term">resample up</dfn> (increase the number of pixels, or <dfn class="term">upsample</dfn>),
new pixels are added. You specify an <dfn class="term">interpolation</dfn>&#160;method
to determine how pixels are added or deleted.</p>
<div class="fignone"><img alt="" id="im_08" src="images/im_08.png" /><div class="figdesc">Resampling pixels</div><br /><dl><dt class="dlterm">A.</dt>
<dd>Downsampled</dd><p class="dlseparator"></p><dt class="dlterm">B.</dt>
<dd>Original</dd><p class="dlseparator"></p><dt class="dlterm">C.</dt>
<dd>Resampled
up (selected pixels displayed for each set of images)</dd><p class="dlseparator"></p></dl>
</div><p>Keep
in mind that resampling can result in poorer image quality. For
example, when you resample an image to larger pixel dimensions,
the image loses some detail and sharpness. Applying the Unsharp
Mask filter to a resampled image can help refocus the image details.</p>
<p>You
can avoid the need for resampling by scanning or creating the image
at a sufficiently high resolution. If you want to preview the effects
of changing pixel dimensions on‑screen or to print proofs at different
resolutions, resample a duplicate of your file. </p>
<p>Photoshop resamples images using an <dfn class="term">interpolation
method </dfn>to assign color values to any new pixels based on
the color values of existing pixels. You can choose which method
to use in the Image Size dialog box.</p>
<dl><dt class="dlterm">Nearest Neighbor</dt>
<dd>A fast but less precise method that replicates the pixels
in an image. This method is for use with illustrations containing
edges that are not anti-aliased, to preserve hard edges and produce
a smaller file. However, this method can produce jagged effects,
which become apparent when you distort or scale an image or perform
multiple manipulations on a selection.</dd><p class="dlseparator"></p><dt class="dlterm">Bilinear</dt>
<dd>A method that adds pixels by averaging the color values of
surrounding pixels. It produces medium-quality results.</dd><p class="dlseparator"></p><dt class="dlterm">Bicubic</dt>
<dd>A slower but more precise method based on an examination
of the values of surrounding pixels. Using more complex calculations,
Bicubic produces smoother tonal gradations than Nearest Neighbor
or Bilinear.</dd><p class="dlseparator"></p><dt class="dlterm">Bicubic Smoother</dt>
<dd>A good method for enlarging images based on Bicubic interpolation
but designed to produce smoother results. </dd><p class="dlseparator"></p><dt class="dlterm">Bicubic Sharper</dt>
<dd>A good method for reducing the size of an image based on Bicubic
interpolation with enhanced sharpening. This method maintains the detail
in a resampled image. If Bicubic Sharper oversharpens some areas
of an image, try using Bicubic.</dd><p class="dlseparator"></p></dl>
<div class="tip"><img src="images/tip_help.png" />You can specify a default interpolation method
to use whenever Photoshop resamples image data. Choose Edit&#160;&gt;
Preferences&#160;&gt; General (Windows) or Photoshop&#160;&gt;
Preferences&#160;&gt; General (Mac&#160;OS), and then choose
a method from the Image Interpolation Methods menu.</div></div>

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