kitepdf-core/io.github.yuroyami.kitepdf.core.render/KiteMaskTransfer

KiteMaskTransfer

The transfer function of a soft mask as a table of 256 levels (ISO 32000-1, 11.6.5.2, Table 144, /TR). The table maps each value of the mask group, its alpha or its luminosity, to the mask value that gates the content. Both run from 0 to 255.

Types

Companion

object Companion

Properties

isNearlyLinear

val isNearlyLinear: Boolean

True when the line of slope and offset stays within one level of the table at every level, so a backend that can only scale and offset gives the right mask.

offset

val offset: Double

The mask value of that line for group value 0, from 0 to 1.

slope

val slope: Double

The slope of the straight line closest to the table, with both axes from 0 to 1. A backend that can only scale and offset a colour, such as a colour matrix, uses slope and offset. The line is exact for a linear function such as an inverter.

Functions

get

operator fun get(level: Int): Int

The mask value for the group value level. A level outside 0 to 255 is clamped.

toByteArray

fun toByteArray(): ByteArray

The table as 256 bytes, for a backend that takes a lookup table.

toMaskAlpha

fun toMaskAlpha(argb: IntArray, luminosity: Boolean)

Turns the pixels of a drawn mask group into mask values, in place, for a backend that gates by pixels because it has no table colour filter. Each pixel of argb, straight ARGB, becomes black with the alpha of its mask value: its luminosity 0.30 R + 0.59 G