Module Hugin_vg

Picture describes drawings and Renderable puts one on a page of a physical size. Three libraries render renderables, each with a render function:

• hugin.vg.raster draws them as RGBA tensors, and as PNG files, at a density in device pixels per point;
• hugin.vg.svg writes them as SVG documents;
• hugin.vg.pdf writes them as PDF documents.

The renderers are separate libraries so that a program links only those it uses; they depend on nx.io for PNG encoding and compression.

Points, boxes, affine maps, paths, stroke styles and colours come from Hugin_gg, whose conventions apply here, and glyph runs from Hugin_font. The meaning of a picture is stated once, in Semantics. Every renderer writes every picture to that meaning, within the accuracy it documents, and no renderer drops or replaces part of a picture. Raster output is the meaning itself; SVG and PDF output show it in viewers that have the features each renderer lists.