wumpus-core: Pure Haskell PostScript and SVG generation.

[ bsd3, graphics, library ] [ Propose Tags ]

Wumpus is a low-level library for generating static 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.

Wumpus makes pictures from paths and text labels. Paths themselves are made from points. The usual affine transformations (rotations, scaling, translations) can be applied to Pictures. 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 and dropped between releases, it has no stable API.

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.

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

There are two major changes between 0.35.0 and 0.36.0.

PrimElement has been removed and the grouping constructor it provided has been moved into the Primitive type. As both types are opaque, definitions in client code will work without change, but all type signatures referencing PrimElement will need to replace PrimElement with Primitive.

Rotations and scalings on Primitives have changed again. Primitives are now instances of the affine classes so support - rotate, rotateAbout, scale, translate. Primitives are now considered to be in the implicit affine frame with origin at (0,0). Previously rotatation on Primitives (via the function rotatePrim) was really a special case to allow slanted text, the rotation was about the text's baseline origin and not the affine frame. As rotation now works differently there is a special constructor for slanted text rtextlabel.

Changelog:

1. 35.0 to 0.36.0:

• API / behaviour change - rotation on primitives changed. New functions have been added to create rotated text labels and ellipses (rtextlabel, rstrokeEllipse, etc.), and Primitives have been made instances of the Affine classes except for the general matrix Transform class. The old functions for transforming Primitives (rotatePrim, scalePrim, etc.) have been removed. The demos (Rotated.hs, Scaled.hs, Translated.hs) have been removed as they pertain to the old behaviour, there are new demos highlighting the new behaviour (TransformEllipse.hs, etc.).

• Major change - removed the PrimElement type. The (opaque) Primitive type has been changed to incorporate a grouping constructor equivalent to PrimElement's XLinkGroup contructor. The change has made the implementation of SVG hyperlinks more efficient, but has forced various type signatures to change in Core.Picture. Client code will also have to change type signatures - PrimElement becomes Primitive.

• Core.PtSize - the class FromPtSize has been given a Num superclass constraint. This can shorten type signatures of functions that use fromPtSize.

• Corrected a bug where textlabels would generate an invalid bounding box and cause a runtime error when supplied with an empty string. Now there is no runtime error - and no-ops are generated in the output.

• Internal changes - moved PrimCTM from Core.PictureInternal into separate module. Moved utility modules into their own directory Utils. Move text modules into their own directory Text.

• Removed dependency on algebra for Semigroup. The equivalent append operation on BoundingBox is boundaryUnion.

• Renamed the Core.GraphicsState to Core.GraphicProps. Moved the property datatypes from Core.PictureInternal into Core.GraphicProps (StrokeProps, LabelProps, etc.).

• Moved wumpus_default_font from Core.Picture into Core.Graphic.Props.