dash-capture 0.0.6

Browser capture & custom renderer pipeline for Plotly Dash components

dash-capture

Plotly figures in Dash are rendered by JavaScript in the browser — the Python server never holds the chart as pixels. dash-capture bridges this gap by triggering the capture directly in the running browser, with no server-side headless browser (Chrome, Playwright, webshot2) required. The result is delivered to Python for post-processing, custom rendering, and download.

Installation

pip install dash-capture

Usage

High-level — one-line wizard with form, preview, and download

from dash_capture import capture_graph, plotly_strategy

# Returns an html.Div — place it next to your dcc.Graph
capture_graph(
    graph="my-graph",
    trigger="Export",
    strip_title=True,
    width=2400,
    height=1600,
)

Clicking the trigger opens a modal with editable fields, a live preview, and a download button.

Low-level — wire capture to your own UI

from dash_capture import capture_binding, plotly_strategy

binding = capture_binding(
    "my-graph",
    strategy=plotly_strategy(strip_title=True, width=2400),
    trigger=Input("my-btn", "n_clicks"),
)

# Place binding.store in the layout
# React to binding.store_id to get the base64 PNG

Custom renderer

def my_renderer(_target, _snapshot_img, title: str = ""):
    """_target: file-like, _snapshot_img: callable → raw PNG bytes."""
    png = _snapshot_img()
    # post-process: add watermark, corporate frame, etc.
    _target.write(png)

capture_graph("my-graph", renderer=my_renderer)

Strategies

Strategy	Method	Use case
plotly_strategy()	Plotly.toImage()	Plotly charts — exact resolution
html2canvas_strategy()	html2canvas	Any DOM element
canvas_strategy()	canvas.toDataURL()	Raw <canvas> elements

Strip patches remove chart decorations before capture without touching the live chart:

plotly_strategy(
    strip_title=True,
    strip_legend=True,
    strip_margin=True,
    width=2400,
    height=1600,
    format="png",   # or "jpeg", "webp", "svg"
)

Pre-filling fields from the live figure

FromPlotly reads a value from the running Plotly figure to pre-populate form fields — no re-typing needed:

from dash_capture import capture_graph, FromPlotly

capture_graph(
    "my-graph",
    title=FromPlotly("layout.title.text"),   # reads current title
    sources="Internal data",
)

License

MIT