Package: cairo

CEnum cairo:operator-t

Declaration

(cffi:defcenum operator-t
  :clear
  :source
  :over
  :in
  :out
  :atop
  :dest
  :dest-over
  :dest-in
  :dest-out
  :dest-atop
  :xor
  :add
  :saturate
  :multiply
  :screen
  :overlay
  :darken
  :lighten
  :color-dodge
  :color-burn
  :hard-light
  :soft-ligth
  :difference
  :exclusion
  :hsl-hue
  :hsl-saturation
  :hsl-color
  :hsl-luminosity)

Values

:clear
Clear destination layer (bounded).
:source
Replace destination layer (bounded).
:over
Draw source layer on top of destination layer (bounded).
:in
Draw source where there was destination content (unbounded).
:out
Draw source where there was no destination content (unbounded).
:atop
Draw source on top of destination content and only there.
:dest
Ignore the source.
:dest-over
Draw destination on top of source.
:dest-in
Leave destination only where there was source content (unbounded).
:dest-out
Leave destination only where there was no source content.
:dest-atop
Leave destination on top of source content and only there (unbounded).
:xor
Source and destination are shown where there is only one of them.
:add
Source and destination layers are accumulated.
:saturate
Like over, but assuming source and dest are disjoint geometries.
:multiply
Source and destination layers are multiplied. This causes the result to be at least as dark as the darker inputs.
:screen
Source and destination are complemented and multiplied. This causes the result to be at least as light as the lighter inputs.
:overlay
Multiplies or screens, depending on the lightness of the destination color.
:darken
Replaces the destination with the source if it is darker, otherwise keeps the source.
:lighten
Replaces the destination with the source if it is lighter, otherwise keeps the source.
:dodge
Brightens the destination color to reflect the source color.
:burn
Darkens the destination color to reflect the source color.
:hard-light
Multiplies or screens, dependent on source color.
:soft-light
Darkens or lightens, dependent on source color.
:difference
Takes the difference of the source and destination color.
:exclusion
Produces an effect similar to difference, but with lower contrast.
:hsl-hue
Creates a color with the hue of the source and the saturation and luminosity of the target.
:hsl-saturation
Creates a color with the saturation of the source and the hue and luminosity of the target. Painting with this mode onto a gray area produces no change.
:hsl-color
Creates a color with the hue and saturation of the source and the luminosity of the target. This preserves the gray levels of the target and is useful for coloring monochrome images or tinting color images.
:hsl-luinosity
Creates a color with the luminosity of the source and the hue and saturation of the target. This produces an inverse effect to the :hsl-color value.

Details

The cairo:operator-t enumeration is used to set the compositing operator for all Cairo drawing operations. The default operator is the :over value. The operators marked as unbounded modify their destination even outside of the mask layer, that is, their effect is not bound by the mask layer. However, their effect can still be limited by way of clipping.

To keep things simple, the operator descriptions here document the behavior for when both source and destination are either fully transparent or fully opaque. The actual implementation works for translucent layers too. For a more detailed explanation of the effects of each operator, including the mathematical definitions, see Cairo's Compositing Operators.
 

See also

cairo:context-t
cairo:operator
2025-1-2