Adobe Photoshop CS4 User Manual

Page 67

USING PHOTOSHOP CS4

Opening and importing images

Last updated 1/10/2010

Resampling pixels
A. Downsampled B. Original C. Resampled up (selected pixels displayed for each set of images)

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.

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.

Photoshop resamples images using an interpolation method 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.

Nearest Neighbor

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.

Bilinear

A method that adds pixels by averaging the color values of surrounding pixels. It produces medium-quality

results.

Bicubic

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.

Bicubic Smoother

A good method for enlarging images based on Bicubic interpolation but designed to produce

smoother results.

Bicubic Sharper

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.