Table 80 – Additional Entries Specific to a Type 2 Shading Dictionary

Key

Type

Value

Coords

array

(Required) An array of four numbers [ x 0 y 0 x 1 y 1 ] specifying the starting and ending coordinates of the axis, expressed in the shading’s target coordinate space.

Domain

array

(Optional) An array of two numbers [ t 0 t 1 ] specifying the limiting values of a parametric variable t. The variable is considered to vary linearly between these two values as the colour gradient varies between the starting and ending points of the axis. The variable t becomes the input argument to the colour function(s). Default value: [ 0.0 1.0 ].

Function

function

(Required) A 1-in, n-out function or an array of n 1-in, 1-out functions (where n is the number of colour components in the shading dictionary’s colour space). The function(s) shall be called with values of the parametric variable t in the domain defined by the Domain entry. Each function’s domain shall be a superset of that of the shading dictionary. If the value returned by the function for a given colour component is out of range, it shall be adjusted to the nearest valid value.

Extend

array

(Optional) An array of two boolean values specifying whether to extend the shading beyond the starting and ending points of the axis, respectively. Default value: [ false false ].