wumpus-core: Pure Haskell PostScript and SVG generation.

[ bsd3, graphics, library ] [ Propose Tags ]

Wumpus - (W)riter (M)onad (P)ost (S)cript.

Wumpus is a kernel library for generating 2D vector pictures, its salient feature is portability due to no FFI dependencies. It can generate PostScript (EPS) files and SVG files. The generated PostScript code is plain [1] and reasonably efficient as the use of stack operations, i.e gsave and grestore, is minimized.

Pictures in Wumpus are made from paths and text labels. Paths themselves are made from points. The usual affine transformations (rotations, scaling, translations) can be applied to geometric objects. Unlike PostScript there is no notion of a current point, Wumpus builds pictures in a coordinate-free style.

GENERAL DRAWBACKS...

For actually drawing pictures, diagrams, etc. Wumpus is very low level. There is a supplemantary package wumpus-basic available that helps create certain types of diagram, but it is experimental - functionality is added an dropped between releases.

Some of the design decisions made for wumpus-core are not sophisticated (e.g. how attributes like colour are handled, and how the bounding boxes of text labels are calculated), so Wumpus might be limited compared to other systems. However, the design permits a fairly simple implementation - which is a priority. Text encoding an exception - I'm not sure how reasonable the design is. The current implementation appears okay for Latin 1 but may be inadequate for other character sets, so I may have to revise it significantly.

$1$ Because the output is simple, straight-line PostScript code, it is possible to use GraphicsMagick or a similar tool to convert Wumpus's EPS files to many other formats (bitmaps).

Changelog:

1. 23.0 to 0.30.0:

• Substantial changes - the output machinery has been heavily modified, the intention was to reduce the use of matrix transformations in SVG output. Though this goal has not been achieved, some code-size improvements in the SVG output have been made.

• The code generation monads have been changed - Wumpus no longer uses a writer monad for code generation, but it will keep the Wumpus name.

• Improved internal pretty printing and added the function printPicture for debugging.

• The Core.Colour module has been simplified to support just one (new) type - RGBi, and the conversion type class PSColour has been eliminated.

• Core.Picture - the type of the frame function has been changed to take a list of Primitives rather than a single Primitive. The function frameMulti which previously provided this functionality has been removed. SVG hyperlinks are now supported for Primitives.

• The default font size has been changed to 14 pt.

• The Path datatype has been renamed PrimPath, likewise Ellipse is now PrimEllispe and Label becomes PrimLabel.

• Core.Geometry now longer defines an affine frame datatype.

• Core.BoundingBox module changed significantly. The corner functions (boundaryBottomLeft, etc.) have been removed, along with the plane functions (leftPlane, etc.). Some functions have been given more verbose names - corners is now boundaryCorners, within is now withinBoundary and union is now boundaryUnion.

1. 22.0 TO 0.23.0:

• Basic.GraphicsState - extracted the font face fields from FontAttr datatype into a separate datatype FontFace.

• Added PtSize a numeric type wrapping Double. This is specifically for text size calculations, vis the Core.FontSize module.

• Changed all functions in Core.FontSize to return PtSize instead of a polymorphic type u (where u is an instance of Fractional). To get to another unit type rather than FontSize use an explicit conversion that scales the value accordingly.

• Added FromPtSize class constraints to various functions in Core.Picture.