Raster¶

from acron.hud import Raster

class Raster(width: int, height: int, *, name: str = 'raster')¶

Bases: Painter

An RGBA raster you draw into, on a card.

Coordinates are a 2D drawing API’s: (x, y) with y growing DOWN from the top-left. Primitives composite “over” with about a pixel of anti-aliasing, computed on the primitive’s bounding box only, so a stroke costs its own size and not the raster’s.

The pixels live in the engine: acron.raster.RasterPainter (C++), which C++ games use directly. The store is bytes, in Acron’s own layout — BGRA, bottom row first, premultiplied — rather than a float image converted on the way out. None of that is micro-optimisation. An instrument redraws every frame and Acron re-sends the whole texture on any change (RUNTIME rule 17), so:

keeping bytes makes upload() a memcpy rather than a conversion of the whole image;
premultiplying makes “over” a single lerp — dst = src*a + dst*(1-a) across all four channels — instead of a per-channel composite with a divide. The card is drawn with M_premultiplied_alpha to match.

The cost is that compositing rounds to 8 bits per layer, which for two or three HUD layers is invisible and for a deep stack would not be — that is what pixel() / pixels() are for when a test wants the image back as floats.

lines() and polyline() take the union of their segments’ coverage and composite it once, so a trace’s joints and a graticule’s crossings do not darken.

Nothing reaches the GPU until upload(), which is a no-op when nothing was drawn since the last one.

Inheritance diagram

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property data: bytes¶

BGRA, bottom row first, premultiplied.

Type:: The store itself

property dirty: bool¶

labels: LabelPool | None¶: Text sink, created by attach(); text() is a no-op without one, which is what a headless raster wants.

painter¶

BGRA, bottom row first, premultiplied — a Acron RAM image, written in place.

Type:: The native painter