term

DPI

Dots per inch: the pixel density of a scan or a print.

DPI shows how many dots fit into an inch of the image. 300 DPI is the usual choice for text recognition: sharp glyphs at a reasonable file size.

Optical character recognition: turning a picture of text into editable text.

An image stored as a grid of pixels, each with its own colour.

A PDF that contains only page images: the text cannot be selected or searched.

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