Image.BlendMode (image v0.62.0)

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Functions to define and validate the blending modes that can be applied when composing images.

Summary

Types

t()

Blend mode to use when compositing images. See Image.compose/3.

Functions

default_blend_mode()

Returns the default blend mode

known_blend_modes()

Returns the known blending modes.

validate_blend_mode(blend_mode)

Normalizes and validates a blend mode.

Types

t()

@type t() ::
  :exclusion
  | :soft_light
  | :hard_light
  | :colour_burn
  | :colour_dodge
  | :lighten
  | :darken
  | :screen
  | :saturate
  | :dest_atop
  | :dest_out
  | :dest_in
  | :dest_over
  | :atop
  | :over
  | :overlay
  | :multiply
  | :dest
  | :source
  | :difference
  | :add
  | :xor
  | :out
  | :in
  | :clear

Blend mode to use when compositing images. See Image.compose/3.

  • :over the image shows what you would expect if you held two semi-transparent slides on top of each other. This is the default when composing images
  • :clear where the second image is drawn, the first is removed
  • :source the second image is drawn as if nothing were below
  • :in the first image is removed completely, the second is only drawn where the first was
  • :out the second is drawn only where the first isn't
  • :atop this leaves the first image mostly intact, but mixes both images in the overlapping area
  • :dest leaves the first image untouched, the second is discarded completely
  • :dest_over like :over, but swaps the arguments
  • :dest_in like :in, but swaps the arguments
  • :dest_out like :out, but swaps the arguments
  • :dest_atop like :atop, but swaps the arguments
  • :xor something like a difference operator
  • :add a bit like adding the two images
  • :saturate a bit like the darker of the two
  • :multiply at least as dark as the darker of the two inputs
  • :screen at least as light as the lighter of the inputs
  • :overlay multiplies or screens colors, depending on the lightness
  • :darken the darker of each component
  • :lighten the lighter of each component
  • :colour_dodge brighten first by a factor second
  • :colour_burn darken first by a factor of second
  • :hard_light multiply or screen, depending on lightness
  • :soft_light darken or lighten, depending on lightness
  • :difference difference of the two
  • :exclusion somewhat like :difference, but lower-contrast

Functions

default_blend_mode()

Returns the default blend mode

Example

iex> Image.BlendMode.default_blend_mode
:VIPS_BLEND_MODE_OVER

known_blend_modes()

Returns the known blending modes.

See Image.BlendMode.t/0 for a description of each mode.

validate_blend_mode(blend_mode)

@spec validate_blend_mode(t() | nil) ::
  {:ok, atom()} | {:error, Image.error_message()}

Normalizes and validates a blend mode.

Argument

Returns

  • {:ok, atom_blend_mode} where atom_blend_mode is a valid blend mode for libvips

  • {:error, reason}

Examples

iex> Image.BlendMode.validate_blend_mode :clear
{:ok, :VIPS_BLEND_MODE_CLEAR}

iex> Image.BlendMode.validate_blend_mode "Over"
{:ok, :VIPS_BLEND_MODE_OVER}

iex> Image.BlendMode.validate_blend_mode :VIPS_BLEND_MODE_XOR
{:ok, :VIPS_BLEND_MODE_XOR}

iex> Image.BlendMode.validate_blend_mode :woops
{:error, {:error, "Unknown blend mode. Found :woops"}}