Diagrams: Difference between revisions

Revision as of 08:19, 17 November 2009

The diagrams library provides an embedded domain-specific language (EDSL) for creating simple pictures and diagrams in Haskell

Rewrite

Core DSL

Style

Do we either want

yellowCircle x y radius = yellowFill $ circleShape x y radius

or

drawYellowCircle x y radius = do $

   setFill yellow
   drawCircle x y radius

?

The first version allows better reuse and functional composition.

Elements

graphical primitives
- path
  - boundingBox
  - moveTo, lineTo, cubic bezier, quadratic bezier, arcTo
- text
  - boundingBox
  - convertToPath
- circle
  - boundingBox
  - convertToPath
- ellipse
  - boundingBox
  - convertToPath
- rectangle
  - boundingBox
  - convertToPath
- polygon
  - boundingBox
  - convertToPath
- polyline
  - boundingBox
  - convertToPath
graphical attributes
- fill
  - paint
    - solid color, gradient, pattern
  - fill rule
    - evenOdd, nonZero
- stroke
  - paint
    - solid color, gradient, pattern
  - width
  - line cap
  - line join
  - miter limit
  - dash
    - offset
    - array
- marker symbols
- effects
  - shadow, blur, turbulence
constraint solving
animations/pages/frames

Data structures

data Figure = Figure {
    fill :: Fill
  , shape :: Shape
  , stroke :: Stroke
  }

data Fill = Fill {
    fillPaint :: Paint,
  }

data Stroke = Stroke {
    strokePaint :: Paint,
  , lineWidth :: Double,
  , dashPattern :: DashPattern
  , lineCap :: LineCap
  , lineJoin :: LineJoin
  , miterLimit :: Double
  } deriving(Eq, Show)

data Paint =
    SolidColor
  | Pattern
  | Gradient
  deriving(Eq, Show)

data LineCap =
    LineCapButt
  | LineCapRound
  | LineCapSquare
  deriving(Eq, Show)

data LineJoin =
    LineJoinMiter
  | LineJoinRound
  | LineJoinBevel
  deriving(Eq, Show)

data Shape =
    Path
  | Primitive
  | Text
  deriving(Eq, Show)

data Path = Path {
    segments :: [Segment]
  }
  deriving(Eq, Show)

data Segment = 
    Move Point
  | Line {
      a :: Point
    , b :: Point
    }
  | HorizontalLine {
      a :: Point
    , w :: Double
    }
  | VerticalLine {
      a :: Point
    , h :: Double
    }
  | QuadraticBezier Point Point Point
  | CubicBezier Point Point Point Point
  deriving(Eq, Show)

data Point =
    Node2d Double Double
  | Node3d Double Double Double
  deriving(Eq, Show)

data Primitive =
    Circle
  | Ellipse
  | Rectangle
  | RegularPolygon
  | Square
  | Star
  deriving(Eq, Show)

class PathLike a =
	convertToPath :: a -> Path

Modules/Extensions

Paths

inset, outset
boolean operations
morphing
approximation (autotrace)

See

Shapes and symbols

stars, supershape, symbols
diagrams
- histograms, density plots

Input/Output

Many Haskell graphic libraries are tied to a specific rendering backend (Cairo, OpenGL, libGD etc) which makes collaboration and reuse of code and data structures very hard or impossible.

Also some dependencies are hard to fulfill. Cairo is very difficult to install on Mac OS 10.6. If you just need to generate PDF diagrams, you could choose the pure HPDF library where e.g. Hieroglyph can not be installed because of its Cairo dependence.

Output

interactive drawing via Cairo
PDF export via pure HPDF
EPS export
SWF export
LaTeX export
exotic backends
- generate Java2d or Processing source code

Input

pure Haskell PNG import via pngload
pure Haskell SVG import

Inspiration

Applications_and_libraries/Graphics

Related non-Haskell projects

Food for thought