wumpus-core: Pure Haskell PostScript and SVG generation.

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 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 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.

\[1\] 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. 31.0 to 0.32.0:

• Major API changes to Core.Picture for XML hyperlinks. Hyperlinks now group one-or-more Primitives (path or label), instead of being attached to a single Primitive. This better corresponds with XML but it has made the Picture type more complicated, and has mandated significant changes to the Picture API. All the hyperlink variants of the Primitive constructors have been removed (xcstroke, xfill, xtextlabel, ...), and hyperlinks are now created with xlinkGroup.

• The type signatures for the primitive constructors (fill, cstroke, textlabel, ...) in the Picture API have changed and are now more complicated as there is an extra layer of indirection in the type hierarchy.

• The primitive constructors for filled and stroked paths and ellipses have been renamed: bordered is now fillStroke, borderedEllipse is now fillStrokeEllipse.

• Core.FontSize - the arguments to the function textBounds have been changed to take the String in question, rather than its precomputed length. The size of the string is then calculated with the new function charCount which takes into account escaped characters.

• Added yellow, cyan and magenta to the predefined colours in Core.Colour.

1. 30.0 to 0.31.0:

• Extended the label type to optionally handle horizontal or vertical "kerning". This can be efficiently implemented in SVG.

• Major API change - the Primitive constructors defined in Core.PictureLanguage are no longer overloaded (cstroke, ostroke, fill, textlabel, ellipse). The respective classes (Stroke, TextLabel, Ellipse) have been removed and the constructors now have monomorphic types. This is because Wumpus-Core now only has one colour type and stroke attributes are now a single type, so polymorphism became less useful (and the simplicity of monomorphic types became more favourable). ellipse is no longer a constructor instead there variants fillEllipse and strokeEllipse.

• Added support for bordered closed paths - i.e. paths that are both stroked and filled. These can be efficiently drawn in SVG with a single path element.

• Changed StrokeAttr representation to be a regular data type rather than a list of deltas - i.e. differences to the graphics state.

• Added SVG font attribute delta optimizations to help reduce SVG code size - via the fontDeltaContext function in Core.Picture. This functionality was partially inplemented in the last release using the GSUpdate datatype - this datatype it is now called FontCtx.

• Some internal work documenting text encoding.

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.

• Added support for hyperlinks in the SVG output.

• 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.

Modules

[Index]

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• Package description (revised from the package)

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Package maintainers

• StephenTetley

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