0.10.0 — Streamlit Components v2 and Fabric.js 7

pip install streamlit-drawable-canvas==0.10.0          # base
pip install "streamlit-drawable-canvas[image]==0.10.0"  # if you read image_data

Rebuilt on Streamlit Components v2 and Fabric.js 7 (from Fabric.js 4.4.0),
replacing the React 16 / CRA v1 frontend.

Breaking

• image_data is now opt-in. Pass return_image_data=True to st_canvas();
  accessing image_data without it raises RuntimeError. Pillow and numpy moved
  out of the base install into the [image] extra: pip install streamlit-drawable-canvas[image].
• Minimum Streamlit is now 1.53; minimum Python is now 3.10.
• background_image works again, and is widened to accept a URL, data: URI, local
  path, raw bytes, or a PIL Image -- the same inputs st.image accepts. It was broken on
  Streamlit >= ~1.5x because it called a private Streamlit API
  (streamlit.elements.image.image_to_url) that had moved and changed signature; the
  new implementation resolves images entirely on the Python side, with no private APIs.
• Object type in json_data is now capitalized. Fabric 7 emits "Rect",
  "Circle", "Line", "Path"; Fabric 4 emitted "rect", "circle", "line",
  "path". Code that branches on obj["type"] == "rect" does not error -- it silently
  stops matching. Compare case-insensitively if you handle payloads from both versions.
• Saved drawings from 0.9.x with circle or point objects render as a thin sliver,
  not the original shape, when fed back in via initial_drawing. Fabric 4 wrote
  Circle.startAngle/endAngle in radians; Fabric 7 reinterprets those same JSON keys
  as degrees, and loadFromJSON doesn't consult the JSON's version field to tell the
  difference. Declared breaking, with no migration shim. Line, Rect, freedraw, Polygon,
  and Transform objects are unaffected.
• An unrecognized drawing_mode now raises ValueError instead of silently falling
  back to "freedraw".

Added

• on_change: an optional callback invoked when the component sends a new drawing.
• background_image_fit: "stretch" (default, the historical behaviour) or "contain",
  which preserves the background image's aspect ratio and centres it inside the canvas
  rather than distorting it to fill. Makes a canvas larger than its background image
  usable, and lets an image keep its proportions.
• disabled: renders the canvas read-only. Drawing, selection and transforms are inert,
  nothing is sent back to Streamlit, and the toolbar is hidden regardless of
  display_toolbar -- undo/redo/reset would otherwise let a viewer mutate a canvas that
  is meant to be read-only. initial_drawing still renders.
• The component renders without an iframe (Streamlit Components v2), and undo/redo
  history now survives an unrelated widget rerun.
• FAQ.md: a reference for the json_data structure and the behaviours that most
  often trip people up -- scaleX/scaleY after a transform, centre-relative Line
  coordinates, the smoothed freedraw path, canvas-versus-source-image coordinates,
  and how to clear the canvas from Python.

Changed

• The toolbar now looks and behaves like a native Streamlit element toolbar. It was a
  row of bare icons pinned below the canvas's bottom-left corner, always visible; it is
  now a floating, shadowed card at the canvas's top-right, above the canvas rather than
  beside it, fading in on hover the way the st.dataframe and chart toolbars do.
  Geometry, radii, hover and active tints all come from the Streamlit theme
  (--st-base-radius, --st-button-radius, --st-text-color,
  --st-background-color), so it tracks light, dark and custom themes -- including the
  two values Streamlit itself varies by theme base, shadow depth and icon opacity. Icons
  are inline SVG on currentColor, replacing the old recolored PNGs. The canvas border
  follows --st-border-color instead of a hardcoded lightgrey.
• The toolbar no longer occupies layout space. The component's height is now exactly
  the height you pass, not height + 32. Incidentally fixes the bin icon sitting close
  enough to the canvas to be hit by accident.
• The send button is renamed "Update the app with this drawing" (was "Send to
  Streamlit") and its icon is now an upload arrow. The old label named the framework
  rather than the effect, on a surface the app's users see; the old glyph was the one
  Streamlit's own toolbars use for "Download as CSV", so it read as "save the image".
  If you drive the button in a test, it is addressed by that new accessible name.
• The toolbar stays pinned open when nothing sends automatically -- that is, when
  update_streamlit=False or drawing_mode="polygon". Hiding it behind a hover would
  hide the only discoverable way to commit a drawing. It is hover-revealed otherwise.

Fixed

• CanvasResult was returned as the class itself rather than an instance when the
  component had no value yet.

Full changelog: https://github.com/andfanilo/streamlit-drawable-canvas/blob/main/CHANGELOG.md