H

halftone

The reproduction of a continuous-tone image, which is made by using a screen that breaks the image into various- sized dots. The resolution, or number of lines per inch (lpi), of a halftone depends on the printer s capabilities. The tonal densities of an image are determined by the size of the dots. The larger the dot, the more ink deposited, and the darker the area appears. When you send an image to a printer, Photoshop, in tandem with the printer driver software, automatically converts the tonal information contained in pixels into dot-density information that the printer uses to construct the image.

halftone screen

Refers to the dot density of a printed image, measured in lines per inch (lpi). A halftone screen, also called screen frequency, is a grid of dots.

highlight

The lightest part of an image, represented on a digital image by pixels with high numeric values or on a halftone by the smallest dots or the absence of dots.

histogram

A graph of the brightness values of an image. The more lines the histogram has, the more tonal values are present in the image. The length of a line represents the relative quantity of pixels of a particular brightness. The taller the line, the more pixels of a particular tonal range the image will contain. Histograms are displayed in Photoshop s Levels and Threshold dialog boxes and the Histogram palette.

History log

A Photoshop CS feature to record the edit history of a work session to a text file, file metadata, or both.

History palette

The Photoshop palette that records all of the changes that you make to an image during a session, as a series of individual states. You can use the History palette to revert to former versions of an image and to create special effects. The History palette also works in conjunction with the History Brush and Art History Brush tools.

hotspot

In an image map, an area that links to another Web page or URL.

HSB color model

A color model that uses hue, saturation, and brightness characteristics to define each color.

HTML (Hypertext Markup Language)

The programming language used to create Web pages.

hue

The color of light that is reflected from an opaque object or transmitted through a transparent one. Hue in Photoshop is measured by its position on a color wheel, from 0 to 360 degrees.