Blendend.Effects (blendend v0.2.0)

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This module contains functions to add effects to geometries.

It currently provides gaussian blur filter and shadow effects on top of it. The NIF implementation is based on https://blog.ivank.net/fastest-gaussian-blur.html.

Gaussian blur is applied after rasterizing a path into an offscreen image, then composited back on the destination canvas. So applying a blur to a shape is more expensive than most other operations in blendend.

Examples:

use Blendend.Draw
clear(fill: rgb(0x42, 0x4D, 0x8C))

ring =
  path do
    add_circle(220, 210, 96.0)
  end

blur_path(ring, 4,
  mode: :stroke,
  stroke: rgb(90, 200, 255),
  stroke_width: 10.0
)

Summary

Types

blur_mode()

Functions

blur_path(canvas, path, sigma, opts \\ [])

Render a blurred copy of path onto canvas.

blur_path!(canvas, path, sigma, opts \\ [])

Same as blur_path/4, but raises on failure and returns the canvas.

shadow_path(canvas, path, dx, dy, sigma, opts \\ [])

Blur a path with an offset to create a soft shadow or glow.

shadow_path!(canvas, path, dx, dy, sigma, opts \\ [])

Same as shadow_path/6, but raises on failure and returns the canvas.

Types

blur_mode()

@type blur_mode() :: :fill | :stroke | :fill_and_stroke | :both

Functions

blur_path(canvas, path, sigma, opts \\ [])

@spec blur_path(Blendend.Canvas.t(), Blendend.Path.t(), number(), keyword()) ::
  :ok | {:error, term()}

Render a blurred copy of path onto canvas.

  • sigma controls blur strength in pixels (roughly radius = 3 * sigma).
  • options:
    • :mode – :fill, :stroke, or :both (alias :fill_and_stroke); (defaults to fill if none set)
    • :offset – {dx, dy} translation before compositing (useful for shadows); values are floats
    • :resolution – scale factor 0 < r ≤ 1.0 to render/blur (If blurring feels slow, tune this down. Defaults to 1.0)

blur_path!(canvas, path, sigma, opts \\ [])

@spec blur_path!(Blendend.Canvas.t(), Blendend.Path.t(), number(), keyword()) ::
  Blendend.Canvas.t()

Same as blur_path/4, but raises on failure and returns the canvas.

shadow_path(canvas, path, dx, dy, sigma, opts \\ [])

@spec shadow_path(
  Blendend.Canvas.t(),
  Blendend.Path.t(),
  number(),
  number(),
  number(),
  keyword()
) ::
  :ok | {:error, term()}

Blur a path with an offset to create a soft shadow or glow.

dx/dy shift the blurred image; other options are forwarded to blur_path/4.

shadow_path!(canvas, path, dx, dy, sigma, opts \\ [])

@spec shadow_path!(
  Blendend.Canvas.t(),
  Blendend.Path.t(),
  number(),
  number(),
  number(),
  keyword()
) ::
  Blendend.Canvas.t()

Same as shadow_path/6, but raises on failure and returns the canvas.