Resizing an image by reducing or increasing its number of pixels. An image can also be resized for printing without resampling and altering its physical structure. If resampling is turned off in the resizing dialog in Photoshop or other image editor, changing the print size changes only the resolution that will be used to convert the image to paper. If the print size is decreased by 50%, the resolution will be increased by 50% and vice versa.
Resizing the Original
Resampling changes the original image. In this Photoshop dialog, selecting Resample Image (bottom left) and changing Height in Pixel Dimensions (in this case, from 660 to 330) means that the original image will be permanently altered.
Resizing for Printing
When resampling is not done, the print resolution can be changed without affecting the original image. In this Photoshop dialog, unchecking Resample Image causes the Pixel Dimensions at the top of the dialog to be grayed, which means the size of the image cannot be modified. Changing Width in Print Size from 7.347 to 5 inches changed the resolution (dots per inch) for the printer only.