Interface IImageRenderer

Namespace

EncDotNet.S100.Maps

Assembly

EncDotNet.S100.Core.dll

Renders the session's current state — loaded datasets, presentation, time, and viewport — to a PNG image. Backs the render_to_image tool.

public interface IImageRenderer

Remarks

This is the seam that makes headless MCP validation possible: an agent can open_dataset → set_palette → render → assert on the bytes with no window and no live render loop. The desktop viewer implements it by snapshotting its live Mapsui map; the CLI implements it over the same headless Skia pipeline its render command already uses — which is why the CLI path runs in CI where a GUI screenshot cannot.

Rendering never mutates session state. The method returns null when there is nothing to render (no viewport / zero size); the calling tool maps that to a not-ready error.

Properties

PreferredSize

The renderer's preferred output size in pixels when the caller omits both dimensions, or null when it has none.

(int Width, int Height)? PreferredSize { get; }

Property Value

(int Width, int Height)?

Remarks

The desktop viewer backs this with its live on-screen viewport size, so an unsized render_to_image matches what the user sees pixel-for-pixel (rather than letterboxing a fixed default against a differently shaped viewport) and can be echoed back so an agent can request a matching aspect ratio or feed the dimensions to a pixel pick. A headless renderer has no on-screen viewport and returns null, leaving the calling tool to apply its fixed default. Default-implemented as null so only hosts with a live viewport need override it.

Methods

RenderToPngAsync(int, int, double, CancellationToken)

Renders the current view to PNG-encoded bytes at the requested size.

Task<byte[]?> RenderToPngAsync(int widthPx, int heightPx, double pixelDensity, CancellationToken cancellationToken = default)

Parameters

widthPx int

Output width in pixels.

heightPx int

Output height in pixels.

pixelDensity double

Display pixel-density multiplier (1.0 = device-independent pixels; 2.0 = HiDPI).

cancellationToken CancellationToken

Cancels the render.

Returns

Task<byte[]>

PNG bytes, or null when there is nothing to render.