# 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 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.

With recent revisions, I've added some extra helper modules that are not really part of the "core", but they provide lists of named colours and safe fonts, plus some code (Extra.PictureLanguage) that has been moved out of the wumpus-core namespace because it is somewhat "higher-level".

WARNING...

With revision 0.18.0, I've changed the internals a bit so that Primitives (paths, text labels) support affine transformations. In the end, this didn't changed the API significantly, though with the next revision, I want to look at changing the PostScript output - swapping some uses of concat to moveto; so again there is the possibility of significant changes between this revision and the next one.

Also the module, Core.BoundingBox, is still a candidate for reworking, as it has too many functions that do not offer distinct functionality. Some functions were removed in revision 0.17.0 and some more are likely to follow.

NOTE...

One consequence of adding affine transformations for primitives is that the bounding box of a primitive under transformation may be tighter than than the bounding box of transformed picture containing the same primitive, i.e.:

liftToPicture (transform PRIM) /= transform (liftToPicture PRIM)

Where liftToPicture is usually frame from Wumpus.Core.Picture.

This is because the bounding box of a transformed picture is calculated by applying the transformation to the corner points of its (previous) bounding box rather than finding the bounding box union of all the composite primitives.

GENERAL DRAWBACKS...

For actually drawing pictures, diagrams, etc. Wumpus is very low level. I'm working on a complementary package wumpus-extra with higher-level stuff (polygons, arrows etc.) but it is too unstable for Hackage. Preview releases can be found at http://code.google.com/p/copperbox/ though.

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 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. 17.0 to 0.18.0:

• Added instances of the affine operation classes (Scale, Rotate ...) for Primitives (path, text label, ellipse).

• Added some picture composition functions to Core.Picture. These are useful for testing where the type class complications of Extra.PictureLanguage are an overhead.

• Added iRGB to Core.Colour - create RGB colours with integer components [0..255] - and iHSB, iGrey.

• Added some test modules for the affine transformations. These illustrate a quirk in Wumpus where, under affine transformation, Pictures may generate a larger bounding box than composite primitives.

• Minor change - ztextlabal changed to use 24pt type rather than 12pt.

• Corrected the cabal file to include the correct files for the manual. The Haskell source file WorldFrame.hs was missing with the generated file WorldFrame.eps incorrectly included instead.

1. 16.0 to 0.17.0:

• Added Core.WumpusTypes to export opaque versions of datatypes from Core.PictureInternal. This should make the Haddock documentation more cohesive.

• Moved the Core.PictureLanguage module into the Extra namespace (Extra.PictureLanguage). This module may change in detail, if not in spirit in the future as I'm not very happy with it. Also this module is somewhat "higher-level" than the modules in wumpus-core, so a different home seems fitting.

• Removed CardinalPoint and boundaryPoint from BoundingBox.

• Argument order of textlabel and ztextlabel changed so that Point2 is the last argument.

• PathSegment constructor names changed - this is an internal change as the constructors are not exported.

• Primitive type changed - moved Ellipse properties into PrimEllipse type - internal change.

• Removed dependency on 'old-time'.

1. 15.0 to 0.16.0:

• Additions to Core.Geometry (direction, pvec, vangle, circularModulo).

• Fixed error with langle due to not accounting for circle quadrants in Core.Geometry.

• Point2 now derives Ord - so it can be used as a key for Data.Map.

• Added escape-character handling to text output in PostScript. This was causing a nasty bug where a drawing would completely fail when special chars shown (GhostView gives little hint of what is wrong when such errors are present).

• Changed BoundingBox operation corners to return a 4-tuple rather than a list.