wumpus-core: Pure Haskell PostScript and SVG generation.

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.

Wumpus-core includes some extra helper modules that are not really part of the "core", but are otherwise currently homeless. They provide lists of named colours and safe fonts, plus some prototype code (Extra.PictureLanguage) for arranging pictures.

WARNING...

The modules Core.BoundingBox and Extra.PictureLanguage are likely to be reworked significantly in the future.

Core.BoundingBox 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.

Extra.PictureLanguage needs some more thought. The current set of classes is rather cumbersome, and some of the operations would benefit new names.

NOTE...

Revision 0.17.0 added affine transformations for primitives (paths, text labels, ellipses), one consequence of this is the bounding box may be tighter for a primitive under affine transformation then lifted to a picture, than a primitive lifted to picture then transformed, i.e.:

boundary (liftToPicture (transform PRIM)) /= boundary (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 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. 18,0 to 0.19.0:

• Added Transform type class to apply a matrix transformation directly.

• Changed the ordering of picture drawing in PostScript and SVG output so the list gets drawn from tail to head with right folds. This makes the list order of pictures match their zorder.

• Renamed the function withinBB (Core.BoundingBox) to within.

• On many type signatures with e.g. Points, I've changed the parameter name on the type constructor from a to u. This is to indicate that u is some unit - almost always a Double. e.g Point2 a becomes Point2 u and all the class obligations change lexically as well Floating a => to Floating u =>. Superficially this means a lot of type signatures have diffs but haven't really changed.

• Added function bezierCircle to generate the Bezier curve points for arcs describing a circle.

• Added new demo - MultiPic. The PostScript it generates is efficient - no extraneous use of concat.

• Added wumpus_default_font constant.

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 - ztextlabel 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.

Modules

[Index]

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• wumpus-core-0.19.0.tar.gz [browse] (Cabal source package)
• Package description (revised from the package)

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Package maintainers

• StephenTetley

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