Method screenshot

marimo/_code_mode/_context.py:1348–1446

Capture a cell's rendered output as a PNG screenshot. Launches a headless Chromium browser (reused across calls) connected to this server in kiosk mode. Requires `playwright` + its Chromium binary:: ctx.install_packages("playwright") # then once: py

(
        self,
        target: int | str | NotebookCell | None = None,
        *,
        timeout_ms: int = 30_000,
        as_data_url: bool = False,
        save_to: str | PathLike[str] | None = None,
    )

    # ------------------------------------------------------------------

    async def screenshot(
        self,
        target: int | str | NotebookCell | None = None,
        *,
        timeout_ms: int = 30_000,
        as_data_url: bool = False,
        save_to: str | PathLike[str] | None = None,
    ) -> bytes | str:
        """Capture a cell's rendered output as a PNG screenshot.

        Launches a headless Chromium browser (reused across calls)
        connected to this server in kiosk mode.

        Requires `playwright` + its Chromium binary::

            ctx.install_packages("playwright")
            # then once: python -m playwright install chromium

        Does **not** require `async with`.

        Args:
            target: Cell to screenshot.

                - `None` — last cell.
                - `int` — cell index (negative OK).
                - `str` — cell ID or name.
                - `NotebookCell` — e.g. `ctx.cells[0]`.

                For an object defined by a cell, resolve first::

                    cid = ctx.find_cell_defining_object(chart)
                    img = await ctx.screenshot(cid)

            timeout_ms: Max wait (ms) for the output to be visible.
            as_data_url: Return `data:image/png;base64,...` str
                instead of raw bytes.
            save_to: Also write the PNG to this path.

        Returns:
            `bytes` (PNG), or `str` (data URL) if *as_data_url*.

        Raises:
            ScreenshotError: Missing playwright, missing browser,
                unknown cell, empty output, or invisible element.
        """
        from pathlib import Path

        from marimo._code_mode.screenshot import (
            ScreenshotError,
            _ScreenshotSession,
            _to_data_url,
        )
        from marimo._messaging.context import HTTP_REQUEST_CTX

        cell_id = self._resolve_screenshot_target(target)

        # Resolve server URL from the current HTTP request context.
        request = HTTP_REQUEST_CTX.get(None)