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Draw Node ​

Purpose & Use Cases ​

The draw node overlays configurable points and lines on top of an input image using normalized coordinates. Rendering happens in the Rosepetal C++ engine, keeping overlays crisp even on high-resolution imagery.

Typical scenarios

  • Visualizing detections (keypoints, landmarks, segmentation anchors)
  • Highlighting measurement locations or points-of-interest
  • Connecting bounding boxes with relational lines
  • Creating quick debugging overlays inside automation flows

Input / Output ​

Input ​

  • Image: Single image object or encoded buffer following the standard toolkit format (data, width, height, channels, colorSpace, dtype).
  • Source path defaults to msg.payload and can be remapped to any msg, flow, or global property.

Output ​

  • Augmented image delivered in raw format (default) or encoded as jpg, png, or webp, matching the rest of the toolkit conventions.
  • Output path defaults to msg.payload.

Configuration ​

I/O ​

  • Input From / Output To: Typed inputs (msg, flow, global) for flexible integration.
  • Output Format: raw, jpg, png, or webp. Quality and PNG optimization options appear when relevant.

Points ​

Each list entry configures one point:

  • X / Y: Normalized coordinates (0.0 – 1.0) with dynamic sources (num, msg, flow, global).
  • Radius: Normalized size relative to the shortest image dimension (minimum 1 pixel).
  • Color: Hex string (e.g. #FF0066). Can be resolved from context if needed.
  • Opacity: Overlay strength (0.0 – 1.0). Combined with any alpha channel supplied in the color.

Click + to add points and 🗑 to remove. Fields keep their typed-input settings, allowing mixed static and dynamic values.

Lines ​

Each list entry defines a polyline segment:

  • Start / End (X1, Y1, X2, Y2): Normalized coordinates.
  • Thickness: Normalized width relative to the shortest dimension (minimum 1 pixel).
  • Color: Hex string or dynamic string.
  • Opacity: Blend factor (0.0 – 1.0).

Debugging ​

  • Debug switch: Streams a preview via the standard Rosepetal debug channel.
  • Debug width: Typed value controlling the preview size.

Runtime Behaviour ​

  1. The node validates the input image using shared node-utils helpers.
  2. Points and lines are resolved via typed inputs—dynamic properties are evaluated per message.
  3. The C++ engine converts normalized coordinates to pixels and composites overlays with anti-aliasing and alpha-aware blending.
  4. Timing information (convert / task / encode) feeds the standard status display.
  5. Optional debug previews reuse the existing toolkit infrastructure (debug-image WebSocket).

Tips & Edge Cases ​

  • Coordinates outside [0, 1] are rejected with warns and skipped.
  • Empty point and line lists pass the image through unchanged.
  • Opacity multiplies the color alpha, so #FF000080 at opacity 0.5 results in 25% final strength.
  • Grayscale inputs are supported; color overlays are converted using luminance weighting.
  • For chained overlays, prefer raw output to avoid repeated re-encoding.

Example Flow ​

[image-in]
   └─▶ [draw]
          • point: x=msg.face.x, y=msg.face.y, radius=0.02, color=#00FFEE
          • line:  x1=0.1, y1=0.9 → x2=0.9, y2=0.9, thickness=0.004, color=#FFAA00
   └─▶ [image-out]

This creates a face marker plus a baseline overlay, fully driven by message content.