chartjs-plugin-annotation

# Polygon Annotations

Polygon annotations are used to mark whatever polygon (for instance triangle, square or pentagon) on the chart area. This can be useful for highlighting values that are of interest.

const options = {
  plugins: {
    annotation: {
      annotations: {
        pentagon: {
          type: 'polygon',
          xValue: 1,
          yValue: 60,
          sides: 5,
          radius: 60,
          backgroundColor: 'rgba(255, 99, 132, 0.25)'
        }
      }
    }
  }
};

# Configuration

# Polygon annotation specific options

The following options are available for polygon annotations.

Name Type Scriptable Default
backgroundShadowColor Color Yes 'transparent'
borderCapStyle string Yes 'butt'
borderJoinStyle string Yes 'miter'
borderWidth number Yes 1
point object Yes {radius: 0}
radius number Yes 10
rotation number Yes 0
sides number Yes 3
xAdjust number Yes 0
xValue number | string Yes undefined
yAdjust number Yes 0
yValue number | string Yes undefined

# Common options to all annotations

The following options are available for all annotations.

Name Type Scriptable Default
adjustScaleRange boolean Yes true
backgroundColor Color Yes options.color
borderColor Color Yes options.color
borderDash number[] Yes []
borderDashOffset number Yes 0
borderShadowColor Color Yes 'transparent'
display boolean Yes true
drawTime string|number Yes 'afterDatasetsDraw'
hitTolerance number Yes 0
init boolean See initial animation undefined
id string No undefined
shadowBlur number Yes 0
shadowOffsetX number Yes 0
shadowOffsetY number Yes 0
xMax number | string Yes undefined
xMin number | string Yes undefined
xScaleID string Yes undefined
yMin number | string Yes undefined
yMax number | string Yes undefined
yScaleID string Yes undefined
z number Yes 0

# General

If one of the axes does not match an axis in the chart, the polygon annotation will take the center of the chart as point. The 2 coordinates, xValue, yValue are optional. If not specified, the polygon annotation will take the center of the scale dimension.

The 4 coordinates, xMin, xMax, yMin, yMax are optional. If not specified, the box is expanded out to the edges in the respective direction and the box size is used to calculated the center of the point. To enable to use the box positioning, the radius must be set to 0 or NaN.

Name Description
adjustScaleRange Should the scale range be adjusted if this annotation is out of range.
display Whether or not this annotation is visible.
drawTime See drawTime.
hitTolerance Amount of pixels to interact with annotations within some distance of the mouse point.
id Identifies a unique id for the annotation and it will be stored in the element context. When the annotations are defined by an object, the id is automatically set using the key used to store the annotations in the object. When the annotations are configured by an array, the id, passed by this option in the annotation, will be used.
radius Size of the polygon in pixels.
rotation Rotation of polygon, in degrees.
sides Amount of sides of polygon.
xAdjust Adjustment along x-axis (left-right) of polygon relative to computed position. Negative values move the polygon left, positive right.
xMax Right edge of the box in units along the x axis.
xMin Left edge of the box in units along the x axis.
xScaleID ID of the X scale to bind onto. If missing, the plugin will try to use the scale of the chart, configured as 'x' axis. If more than one scale has been defined in the chart as 'x' axis, the option is mandatory to select the right scale.
xValue X coordinate of the polygon in units along the x axis.
yAdjust Adjustment along y-axis (top-bottom) of polygon relative to computed position. Negative values move the polygon up, positive down.
yMax Bottom edge of the box in units along the y axis.
yMin Top edge of the box in units along the y axis.
yScaleID ID of the Y scale to bind onto. If missing, the plugin will try to use the scale of the chart, configured as 'y' axis. If more than one scale has been defined in the chart as 'y' axis, the option is mandatory to select the right scale.
yValue Y coordinate of the polygon in units along the y axis.
z The z property determines the drawing stack level of the polygon annotation element. All visible elements will be drawn in ascending order of z option, with the same drawTime option.

# Styling

Name Description
backgroundColor Fill color.
backgroundShadowColor The color of shadow. See MDN (opens new window).
borderColor Stroke color.
borderCapStyle Cap style of the border of polygon. See MDN (opens new window).
borderDash Length and spacing of dashes. See MDN (opens new window).
borderDashOffset Offset for line dashes. See MDN (opens new window).
borderJoinStyle Border line join style. See MDN (opens new window).
borderShadowColor The color of the border shadow. See MDN (opens new window).
borderWidth Stroke width.
shadowBlur The amount of blur applied to shadow. See MDN (opens new window).
shadowOffsetX The distance that shadow will be offset horizontally. See MDN (opens new window).
shadowOffsetY The distance that shadow will be offset vertically. See MDN (opens new window).

# Point

Polygon consists of points. These points are actually Point Annotations and all of the styling options can be configured. General options affecting the location of the point are ignored.

Namespace: options.annotations[annotationID].point, it defines options for the callout on the annotation label.

const options = {
  plugins: {
    annotation: {
      annotations: {
        pentagon: {
          type: 'polygon',
          xValue: 1,
          yValue: 60,
          sides: 4,
          radius: 60,
          backgroundColor: 'rgba(255, 99, 132, 0.25)',
          point: {
            radius: 10,
            borderWidth: 2,
            borderColor: '#666',
            backgroundColor: 'rgba(99, 132, 255, 0.25)',
          }
        }
      }
    }
  }
};

# Element

The following diagram is showing the element properties about a 'polygon' annotation:

polygon

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