[nighthawk]

Why

GeoProjector#45 taught drawSVG to composite tiled base maps in pure Swift so the Lambda can drape MapTiler tiles under Maparoni's renders. The single-image BaseMap (NASA Blue Marble / Black Marble in equirectangular) still lived only in the CoreGraphics code and was skipped by the SVG writer. World- and continent-scale renders, where street tiles look busy, need the Marble look on Linux too, and that is the blocker for the thumbnails and projected-view-mode directions in Maparoni.

What

• The inverse-projection sampler moves to a pure-Swift renderBaseMapBitmap, mirroring the tile compositor. The CoreGraphics renderer wraps its bitmap in a CGImage, so there is one sampler for both paths. Works with any target projection (orthographic, Equal Earth, Mercator, ...), since the pixel lookup goes through projection.inverse and the source projection's forward transform.
• drawSVG embeds .baseMap as a base64 PNG <image> at the drawer's size times pixelDensity, in content order alongside .tiledBaseMap.
• BaseMapImage.decode(pngData:) and BaseMap(pngData:) decode PNGs through swift-png on every platform. The README documents that Linux has no JPEG decoder (convert NASA's JPEG once) and the memory cost: 4096×2048 is about 32 MB resident.
• Tests: BaseMapSVGTests renders a synthetic quadrant-coloured equirectangular image under a world-scale orthographic and a Mercator drawer, decodes the embedded PNG and checks that the colours land where the inverse projection says, that corners outside the globe are transparent, that pixelDensity scales the raster, and that the PNG decoder round-trips. The existing CoreGraphics BaseMapTests still pass through the refactored wrapper.

Verified with swift test on macOS and in swift:6.3-amazonlinux2023 (82 tests pass). No consumer pins bumped; GeoLogicKit and Lambdaroni follow up separately.

Manual testing

Render a real Blue Marble on Linux, e.g. in the Lambda or a scratch executable:

let marble = try GeoDrawer.BaseMapImage.decode(pngData: Data(contentsOf: url))!
let drawer = GeoDrawer(size: .init(width: 800, height: 800), projection: Projections.Orthographic())
let svg = drawer.drawSVG([.baseMap(.init(image: marble))], mapBackground: nil, mapOutline: .init(red: 0, green: 0, blue: 0, alpha: 1))

Open the SVG (or rsvg-convert it): the globe should show the Americas facing you, continents in the right place relative to the outline, and the corners transparent.

🤖 Generated with Claude Code