Cauldron2D.Blend (Cauldron2D v0.2.2)

Source-over compositing of two equal-sized RGBA rectangles.

Cauldron2D.Blend.over(beneath, above)

Both binaries are four bytes per pixel and must be the same length. The result is the same length: above laid over beneath, premultiplied by above's alpha.

available?/0 says whether the C library loaded. Where it did not the same picture is produced in Elixir, some fifty times slower.

Summary

Functions

available?()

Whether the library is loaded and compositing is done in C.

draw(canvas, arg1, picture, arg2, placement, opts \\ [])

picture drawn over canvas, both RGBA, placed by placement, as a new canvas.

over(beneath, above)

above laid over beneath, both RGBA of the same length.

render_band(width, top, bottom, background, items)

The rows top up to bottom of a canvas width pixels wide, starting as background — four RGBA bytes repeated, or those rows' own pixels — with each of items drawn over it in order. An item is {picture, picture_width, picture_height, transform}, transform as transform/1 builds it. The rows are drawn exactly as the same rows of the whole canvas would be.

sized!(rgba, width, height, name)

Raises ArgumentError unless rgba is a picture of width by height pixels, both positive, four bytes each. name says what the picture is in the message.

transform(placement)

The 104-byte transform placement (as draw/6 takes it) is drawn with.

Functions

available?()

@spec available?() :: boolean()

Whether the library is loaded and compositing is done in C.

draw(canvas, arg1, picture, arg2, placement, opts \\ [])

@spec draw(
  binary(),
  {pos_integer(), pos_integer()},
  binary(),
  {pos_integer(), pos_integer()},
  map(),
  keyword()
) :: binary()

picture drawn over canvas, both RGBA, placed by placement, as a new canvas.

placement is a map:

:position — {x, y}, the canvas pixel the picture's origin lands on; fractions allowed
:origin — {x, y} in the picture's pixels, default {0, 0}
:scale — {x, y}, default {1, 1}; a negative scale mirrors along that axis and a zero scale draws nothing
:angle — degrees, counter-clockwise as seen on the canvas, default 0
:blend — {r, g, b} multiplied into the picture's colours, default white
:alpha — 0.0–1.0 multiplied into the picture's alpha, default 1.0
:mode — :over (the default), :add or :subtract; or {:gamemaker, mode}, the same blend with GameMaker's blend factors applied to the alpha channel as well as the colours, as GameMaker draws onto a surface: over colour × As + beneath × (1 − As) and alpha As² + Ad × (1 − As); add colour × As + beneath and alpha As² + Ad; subtract beneath × (1 − colour) and alpha Ad × (1 − As)

Every canvas pixel whose centre falls inside the turned and scaled picture takes the nearest picture pixel, laid over the canvas as over/2 lays one pixel over another — or, with mode: :add, its colour times its alpha added to the canvas's, each channel at most 255, as GameMaker's additive blend mode adds it — or, with mode: :subtract, each canvas channel times one less the picture's colour times its alpha, the canvas's alpha kept, as GameMaker's bm_subtract takes it away. Pixels outside the canvas are dropped. native: false draws in Elixir where the C library is loaded.

over(beneath, above)

@spec over(binary(), binary()) :: binary()

above laid over beneath, both RGBA of the same length.

render_band(width, top, bottom, background, items)

@spec render_band(
  pos_integer(),
  non_neg_integer(),
  non_neg_integer(),
  binary(),
  list()
) :: binary()

sized!(rgba, width, height, name)

@spec sized!(binary(), integer(), integer(), String.t()) :: :ok

Raises ArgumentError unless rgba is a picture of width by height pixels, both positive, four bytes each. name says what the picture is in the message.

transform(placement)

@spec transform(map()) :: binary()

The 104-byte transform placement (as draw/6 takes it) is drawn with.