Key concept: Resample

Resample

Changing the pixel dimensions of an image is called resampling. Resampling can degrade image quality. Downsampling decreases the number of pixels in the image, while upsampling increases the number.

The detail in the original image (left) is crisp, while the detail in the upsampled version (center) is slightly blurred. Much of the detail in the downsampled version (right) is lost.

	Pixel dimensions	Size	File size
Left image	470 x 1000	2.0” x 4.2” at 240 ppi	1.34MB
Center image	940 x 2000	2.0” x 4.2” at 480 ppi	5.38MB
Right image	157 x 333	2.0” x 4.2” at 80 ppi	153K

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