chromacrop

A Viam camera module that dynamically crops a camera feed to a color-detected border region. Point it at any colored tape, border, or marker and it crops the frame to just that region.

Configuration

Add this module as a camera component. Required and optional attributes:

Attribute	Type	Required	Default	Description
source	string	yes	—	Name of the upstream camera to read from
detect_color	string	yes	—	Hex color to detect (e.g. "#dcfe79" for lime green)
hue_tolerance_pct	float	no	0.05	How much hue variation to allow (0.0–1.0, percentage of hue wheel)
segment_size_px	int	no	100	Minimum contour area in pixels (filters noise)
padding	int	no	5	Extra pixels around the detected region

Example config

{
  "source": "my-webcam",
  "detect_color": "#dcfe79",
  "hue_tolerance_pct": 0.05,
  "segment_size_px": 100,
  "padding": 5
}

How it works

1. Reads a frame from the source camera
2. Converts the target hex color to HSV and builds a detection range
3. Thresholds the frame for that color, finds contours
4. Crops to the bounding box of the largest contour (the colored border)
5. Returns the cropped frame as a JPEG

If no matching color is detected, the full uncropped frame is returned as a fallback.

Requirements

• viam-sdk
• opencv-python-headless
• Pillow
• numpy