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Spot Color Detector

The Spot Color Detector analyzes video frames to detect specific colors within defined circular regions. When a color changes, it triggers AXIS events that can be used in rules or captured by Flow nodes.

Overview

Define circular "spots" on the video feed and configure a color palette. The system continuously analyzes each spot and detects which palette color is currently visible. When the color changes, an AXIS event is fired.

Use Cases:

  • Traffic light detection (red/yellow/green states)
  • Status indicator monitoring (LED colors on equipment)
  • Industrial process monitoring (color-coded stages)
  • Presence detection based on color changes

Getting Started

  1. Navigate to Spot Color Detector from the feature menu
  2. The live video preview loads automatically
  3. Click Add Circle to create a detection region
  4. Position and resize the circle over the target area
  5. Configure the color palette with expected colors
  6. Start the feature to begin detection

Configuration

Video Settings

Setting Description
Video Channel Select the video channel (default: 1)
Resolution Analysis resolution (lower = faster processing)
Hysteresis Threshold Color distance threshold to prevent flickering (10-100)

Circle Triggers

Each circle defines a circular detection region:

Property Description
Name Unique identifier for the circle (used in events)
Position X/Y center coordinates (drag to move)
Radius Detection area size (drag corner to resize)

Adding Circles:

  1. Click Add Circle button
  2. Enter a name for the circle (e.g., "traffic_light_1")
  3. Drag the circle to position it over the target
  4. Resize using the corner handle

Editing Circles:

  • Click the pencil icon to rename
  • Click the trash icon to delete
  • Drag to reposition
  • Drag the resize handle to change size

Rectangle Triggers

Rectangles provide flexible detection regions that can handle lens distortion better than circles.

Property Description
Name Unique identifier for the rectangle (used in events)
Position Top-left corner coordinates (drag to move)
Size Width and height (drag corner to resize)

Adding Rectangles:

  1. Click Add Rectangle button
  2. Enter a name for the rectangle
  3. Drag to position it over the target
  4. Resize by dragging the corners

When to Use Rectangles:

  • Detection areas near the edges of the image (where lens distortion is strongest)
  • Rectangular indicators or displays
  • When you need to match the shape of the target area precisely

Color Palette

The palette defines which colors the system recognizes:

Default Colors: - Basic: Red, Green, Blue, Yellow, Orange, Purple, Cyan, Magenta, White, Black, Gray - Traffic: Traffic Red, Traffic Yellow, Traffic Green, Off/Dark

Managing Colors:

Action How To
Add Color Click "Add Color", pick a color and enter a name
Add Detected Click "Add to Palette" on a circle's detected color
Remove Color Click the X on a color chip
Reset Palette Click "Reset" to restore defaults

How It Works

Color Detection

  1. The system captures video frames at the configured resolution
  2. For each circle, pixels within the boundary are sampled
  3. The dominant color (average RGB) is calculated
  4. This color is matched to the nearest palette color
  5. If the color changed beyond the hysteresis threshold, an event fires

Hysteresis

The hysteresis threshold prevents rapid flickering between similar colors:

  • Low value (10-20): More sensitive, may flicker in variable lighting
  • High value (50-100): More stable, requires larger color differences
  • Default (30): Balanced for most scenarios

The threshold represents Euclidean distance in RGB color space.

Processing Time

The UI displays processing time per frame:

  • Green: Under budget, system running smoothly
  • Red: Over budget, consider reducing resolution or circle count

Events

Individual Trigger Events

Each circle and rectangle generates an AXIS event when its color changes:

Event Name: {trigger_name}_state

Event Data:

Field Description
trigger_name Name of the circle or rectangle
color_name Matched palette color name
confidence Match confidence (0-1)

Combined Events

Combined events fire whenever any trigger changes state, providing all trigger states in one event:

Event Name Description
all_circles_state State of all circle triggers
all_rects_state State of all rectangle triggers

Combined Event Data:

Each combined event includes individual color fields for every trigger:

Field Description
{trigger_name}_color Current color for each trigger
{trigger_name}_confidence Match confidence for each trigger

This allows you to capture the state of all triggers in a single event subscription.

Using Events in AXIS Rules

While the Spot Color Detector is running, events appear in the AXIS event system:

  1. Open the device's web interface
  2. Go to System > Events
  3. Find events under the Missing Features ACAP
  4. Create rules triggered by color state changes

Using Events in Flow

Use the Axis Metadata Event (Subscribe) node to receive color change events:

  1. Add the subscribe node to your flow
  2. Select the Spot Color Detector event
  3. Wire the outputs to your logic

Live Preview

The preview shows:

  • Real-time video feed via WebCodecs (no NAT/firewall issues)
  • Circle and rectangle overlays with current state
  • For each trigger:
  • Trigger name
  • Detected color (actual RGB from frame)
  • Matched color (nearest palette color)
  • Edit/Delete controls

Controls

Button Action
Add Circle Create new circular detection region
Add Rectangle Create new rectangular detection region
Show/Hide Toggle overlay visibility
Fullscreen Expand preview to full screen

Best Practices

Circle Placement

  • Position circles directly over the color area
  • Avoid edges where background colors might interfere
  • Use smaller circles for precise targets (LEDs, indicators)
  • Use larger circles for areas with color variation

Palette Configuration

  • Add only colors you expect to detect
  • Use specific shades (e.g., "Traffic Red" vs generic "Red")
  • Test detection and adjust palette colors if needed
  • Add the "Off/Dark" color for inactive states

Performance

  • Use lower resolution for faster processing
  • Limit the number of circles (each adds processing time)
  • Monitor the processing time indicator
  • Increase hysteresis if colors flicker

Troubleshooting

Issue Solution
Color not detected Ensure the palette includes a similar color
Flickering between colors Increase the hysteresis threshold
Wrong color matched Add a more specific color to the palette
High processing time Reduce resolution or circle count
Events not firing Check that the feature is started