FrenchCurve.Draw (FrenchCurve v0.2.1)

Rasterises lines, rectangles and circles into a FrenchCurve.Raster.

Every function takes a raster as its first argument and returns a new one, so calls compose in a pipeline. Coordinates are integer pixels, {0, 0} at the top left, and may fall outside the raster: the parts that land inside are drawn and the rest is clipped. Colours are {r, g, b, a} byte tuples written opaquely, with no blending against what is already there.

Outlines are written as one batch of pixels and filled shapes as one batch of horizontal spans, so a call costs one raster update however many pixels it covers.

FrenchCurve.Raster.new(40, 20)
|> FrenchCurve.Draw.rect({0, 0}, {39, 19}, {80, 80, 80, 255})
|> FrenchCurve.Draw.fill_circle({20, 10}, 6, {255, 0, 0, 255})

Summary

Types

column()

coord()

Functions

circle(raster, arg, radius, color)

Draws a one-pixel-wide circle outline of radius pixels around the centre {cx, cy}.

fill_circle(raster, arg, radius, color)

Fills a disc of radius pixels around the centre {cx, cy}.

fill_columns(raster, columns, color)

Fills vertical columns, each {x, y_from, y_to} with both ends inclusive and in either order.

fill_polygon(raster, points, color)

Fills the polygon whose corners are points, edges included.

fill_rect(raster, arg1, arg2, color)

Fills every pixel of the rectangle spanned by two opposite corners, edges included.

line(raster, from, to, color)

Draws a one-pixel-wide line between the two endpoints, both inclusive.

line_points(arg1, arg2)

Returns the pixels of the one-pixel-wide line between two endpoints, both inclusive, in walking order from from to to.

polyline(raster, points, color)

Draws a connected run of line segments through points in order.

rect(raster, arg1, arg2, color)

Draws the four edges of the rectangle spanned by two opposite corners.

Types

column()

@type column() :: {integer(), integer(), integer()}

coord()

@type coord() :: {integer(), integer()}

Functions

circle(raster, arg, radius, color)

@spec circle(
  FrenchCurve.Raster.t(),
  coord(),
  non_neg_integer(),
  FrenchCurve.Raster.color()
) ::
  FrenchCurve.Raster.t()

Draws a one-pixel-wide circle outline of radius pixels around the centre {cx, cy}.

radius must be a non-negative integer. The interior is untouched.

fill_circle(raster, arg, radius, color)

@spec fill_circle(
  FrenchCurve.Raster.t(),
  coord(),
  non_neg_integer(),
  FrenchCurve.Raster.color()
) ::
  FrenchCurve.Raster.t()

Fills a disc of radius pixels around the centre {cx, cy}.

radius must be a non-negative integer.

fill_columns(raster, columns, color)

@spec fill_columns(FrenchCurve.Raster.t(), [column()], FrenchCurve.Raster.color()) ::
  FrenchCurve.Raster.t()

Fills vertical columns, each {x, y_from, y_to} with both ends inclusive and in either order.

Columns may repeat an x or overlap; the union is filled. The columns are written as horizontal spans in one raster update.

fill_polygon(raster, points, color)

@spec fill_polygon(
  FrenchCurve.Raster.t(),
  [{number(), number()}],
  FrenchCurve.Raster.color()
) ::
  FrenchCurve.Raster.t()

Fills the polygon whose corners are points, edges included.

The polygon is closed from the last point back to the first. Points may be fractional; a pixel is filled when its centre lies inside, using the even-odd rule, and the outline is drawn as well so thin shapes are never lost. Fewer than three points draw as a polyline.

fill_rect(raster, arg1, arg2, color)

@spec fill_rect(FrenchCurve.Raster.t(), coord(), coord(), FrenchCurve.Raster.color()) ::
  FrenchCurve.Raster.t()

Fills every pixel of the rectangle spanned by two opposite corners, edges included.

Both corners are inclusive and may be given in any order.

line(raster, from, to, color)

@spec line(FrenchCurve.Raster.t(), coord(), coord(), FrenchCurve.Raster.color()) ::
  FrenchCurve.Raster.t()

Draws a one-pixel-wide line between the two endpoints, both inclusive.

Handles any direction, including purely horizontal, vertical and single-point lines.

line_points(arg1, arg2)

@spec line_points(coord(), coord()) :: [coord()]

Returns the pixels of the one-pixel-wide line between two endpoints, both inclusive, in walking order from from to to.

polyline(raster, points, color)

@spec polyline(FrenchCurve.Raster.t(), [coord()], FrenchCurve.Raster.color()) ::
  FrenchCurve.Raster.t()

Draws a connected run of line segments through points in order.

A single point plots that pixel and an empty list leaves the raster unchanged. Points are not closed back to the first one; pass the first point again to close the shape.

rect(raster, arg1, arg2, color)

@spec rect(FrenchCurve.Raster.t(), coord(), coord(), FrenchCurve.Raster.color()) ::
  FrenchCurve.Raster.t()

Draws the four edges of the rectangle spanned by two opposite corners.

Both corners are inclusive and may be given in any order. The interior is untouched.