EncDotNet.S100.Renderers.Skia 0.20.0

EncDotNet.S100.Renderers.Skia

Coverage and vector rendering to SkiaSharp bitmaps.

Overview

This library renders S-100 coverage and vector data to SkiaSharp bitmaps. It handles pure rasterization without a map control. Key types include:

• SkiaCoverageRenderer — ICoverageRenderer<SKBitmap> implementation that maps coverage grid cells to pixel colors.
• SkiaSvgRasterizer — rasterizes SVG portrayal symbols to tiled pattern bitmaps.
• SkiaColorExtensions — helpers for converting between RgbaColor and SKColor.

Shared vector rendering core (now EncDotNet.S100.Rendering.Scene)

The backend-agnostic S-100 Part 9 vector rendering core — VectorScene, PaintOp, VectorSceneBuilder, ColorResolver, ScaleVisibility, and WebMercator — has been promoted to its own neutral assembly, EncDotNet.S100.Rendering.Scene, so every rendering backend (this library, EncDotNet.S100.Renderers.Mapsui, and the tiled/async render subsystem) depends on the IR without diamonding through Renderers.Skia. It lowers a display list into a resolved, projected intermediate representation (IR) so the portrayal-correctness logic lives in exactly one place:

• VectorSceneBuilder (in Rendering.Scene) — lowers a DrawingInstruction list + IFeatureGeometryProvider into an ordered VectorScene of PaintOps: applies S-100 Part 9 draw ordering, colour/symbol/line-style resolution, mm→px conversion (1 px = 0.32 mm), text-anchor selection, and the lat/lon → EPSG:3857 projection half.
• PaintOp / VectorScene (in Rendering.Scene) — the IR. PaintOp coordinates are EPSG:3857 metres; all sizes are logical display pixels (resolution-independent). See the PaintOp XML docs for the full unit contract.
• SkiaDisplayListRenderer (in this library, …Renderers.Skia.Scene) — VectorScene + Viewport → SKBitmap. The vector analogue of SkiaCoverageRenderer, suitable for a tile-serving web API with no Mapsui/GUI dependency. It supplies the second projection half (EPSG:3857 → screen) via a Viewport-derived affine. Parsed symbol pictures are cached process-wide (keyed by the resolved SVG), point/text ops whose anchor falls outside the viewport (plus PointCullMarginPx) are culled before any per-op work, and text drawing pools its SKFont/SKPaint per render — all three matter for the tiled subsystem's per-frame overlay, which replays this renderer live every frame. RenderOnto takes an optional cull rectangle so a caller that rotates the canvas can expand it to the rotated viewport's bounding box, plus an OverlayDrawOptions overload that adds the live Label-plane behaviour: a suppressed-text set (from LabelDeclutterer), a screen-space text anchor-rotation that keeps glyphs upright under a rotated viewport while pinning the anchor to its feature, point/text draw filters, and per-run glyph fallback in DrawText (so codepoints the primary face lacks are drawn via SKFontManager.MatchCharacter instead of .notdef tofu boxes).
• LabelDeclutterer (…Renderers.Skia.Scene) — deterministic, priority-driven S-100 Part 9 overlap avoidance for the live label plane. Given a VectorScene it returns the set of TextPaintOps to suppress: point symbols reserve their screen footprints first, then text is placed highest-priority-first against a uniform screen-bucket index, with labels yielding to symbols and to higher-priority labels. Pure and machine-independent.
• OverlayDrawOptions (…Renderers.Skia.Scene) — the options bag for the RenderOnto overlay pass (cull bounds, suppressed text, text anchor-rotation + screen centre, and point/text draw filters).
• WebMercator (in Rendering.Scene) — EPSG:3857 forward projection (matches Mapsui's SphericalMercator.FromLonLat; a parity test asserts agreement).
• ScaleVisibility (in Rendering.Scene) — shared S-100 Part 9 §11.1 scale-visibility rule.
• ColorResolver — S-100 colour-token resolution (palette + inline hex).

Scope (spike): the IR currently covers point, line, solid-area, and text ops. Pattern fills, antimeridian crossing, and Web-Mercator pole limits are not yet represented in the IR — pattern fills remain handled by the Mapsui renderer's dedicated pattern collection / priority-clip / insert phase.

Installation

dotnet add package EncDotNet.S100.Renderers.Skia

Linux arm64 native dependency

When you publish a linux-arm64 executable that uses this renderer, reference the self-contained SkiaSharp native in your application project:

<ItemGroup>
  <PackageReference Include="SkiaSharp.NativeAssets.Linux" ExcludeAssets="all" />
  <PackageReference Include="SkiaSharp.NativeAssets.Linux.NoDependencies" />
</ItemGroup>

The regular SkiaSharp.NativeAssets.Linux arm64 libSkiaSharp.so declares undefined uuid_* / FT_Get_BDF_Property symbols that abort once fontconfig/freetype load on a normal arm64 host, so any render path crashes with undefined symbol: …. The …NoDependencies build is self-contained and renders on both x64 and arm64. Native RID asset selection belongs to the final executable, so this library does not apply the swap to your build. See issue #23.

Text labels render without any system font infrastructure: this package embeds an Open Sans face (Apache-2.0) used as a fallback when the host exposes no usable system font (e.g. the NoDependencies native on a box without fontconfig).