EDOBE XDOM TPC Technical Information download pdf (Page 30)

CHAPTER 3: Scripting Illustrator Measurement units 30

Measurement units

Illustrator uses points as the unit of measurement for almost all distances. One inch equals 72 points. The

exception is values for properties like

kerning, tracking, and the aki properties (used for Japanese text

composition), which use em units. (See “

Em space units” on page 30.)

Illustrator uses points when communicating with your scripts regardless of the current ruler units. If your

script depends on adding, subtracting, multiplying, or dividing specific measurement values for units

other than points, it must perform any unit conversions needed to represent your measurements as

points. For example, to use inches for coordinates or measurement units, you must multiply all inch values

by 72 when entering the values in your script.

The following table shows conversion formulas for various units of measurement:

JavaScript provides the

UnitValue object type, which offers unit-conversion utilities. For details, see

JavaScript Tools Guide.

Em space units

Values that use em units instead of points are measured in thousandths of an em.

An em is proportional to the current font size. For example, in a 6-point font, 1 em equals 6 points; in a

10-point font, 1 em equals 10 points. In a 10-point font, a kerning value of 20 em units is equivalent to:

(20 units x 10 points) / 1000 units/em = 0.2 points

Page-item positioning and dimensions

Illustrator uses simple, two-dimensional geometry in the form of points to record the position of

page item objects in a document. Every page item object in a document has a position property that

defines a fixed point as a pair of page coordinates in the format [x, y]. The fixed point is the top-left corner

of the object’s bounding box.

For information on the types of objects that comprise the

page items collection, see “The artwork tree” on

page 20.

A point is designated by a pair of coordinates:

X The horizontal position, x

X The vertical position, y

Unit Conversion formula

centimeters 28.346 points = 1 centimeter

inches 72 points = 1 inch

millimeters 2.834645 points = 1 millimeter

picas 12 points = 1 pica

Qs 0.709 point = 1 Q (1 Q equals 0.23 millimeter)

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EDOBE XDOM TPC Technical Information Page 30