Labeling objects

Overview

This topic discusses the JSON labeling objects as returned by the REST API.

The following objects are discussed:

• Label placement
• Label class
• Labeling info

Label placement

Label placement is represented as a literal string. It specifies the placement of the label with respect to that of its feature. The following table lists label placement values categorized by the geometry type of the feature:

Label placement values for point features
esriServerPointLabelPlacementAboveCenter	esriServerPointLabelPlacementAboveLeft	esriServerPointLabelPlacementAboveRight
esriServerPointLabelPlacementBelowCenter	esriServerPointLabelPlacementBelowLeft	esriServerPointLabelPlacementBelowRight
esriServerPointLabelPlacementCenterCenter	esriServerPointLabelPlacementCenterLeft	esriServerPointLabelPlacementCenterRight
Label placement values for line features
esriServerLinePlacementAboveAfter	esriServerLinePlacementAboveAlong	esriServerLinePlacementAboveBefore
esriServerLinePlacementAboveStart	esriServerLinePlacementAboveEnd
esriServerLinePlacementBelowAfter	esriServerLinePlacementBelowAlong	esriServerLinePlacementBelowBefore
esriServerLinePlacementBelowStart	esriServerLinePlacementBelowEnd
esriServerLinePlacementCenterAfter	esriServerLinePlacementCenterAlong	esriServerLinePlacementCenterBefore
esriServerLinePlacementCenterStart	esriServerLinePlacementCenterEnd
Label placement values for polygon features
esriServerPolygonPlacementAlwaysHorizontal

Label class

A label class specifies the label definition for a given scale range.

New in 10.1

• where—Use where to determine the features that are labeled with the label class that contains it.

• Use labelExpression to adjust the formatting of labels. A label expression is limited to a single line of code. Apart from specifying a string value or an attribute field value, the following keywords are supported:

  Keyword	Description
  CONCAT	Concatenate two values. Example "\"State: \" CONCAT [State_Name]"
  NEWLINE	Insert a new line. Example "\"State: \" CONCAT NEWLINE CONCAT [State_Name]"
  UCASE([Field])	Convert string value to uppercase string. Example "\"State: \" CONCAT UCASE([State_Name])"
  LCASE([Field])	Convert string value to lowercase string. Example "\"State: \" CONCAT LCASE([State_Name])"
  ROUND([Field], n)	Round a decimal number to set number of decimals as specified by (n). Example "\"Area: \" CONCAT ROUND([Area], 3)"
  FORMATDATETIME([Field], "FormatString")	Format a date/time value with the specified format (FormatString*). The following keywords are recognized: d—Day of the month ddd—Abbreviated day of the week dddd—Full day of the week M—Month in number MMM—Abbreviated month name MMMM—Full month name y—Two-digit year yyyy—Four-digit year h—Hour in 12-hour format H—Hour in 24-hour format m—Two-digit minute s—Two-digit second Example "\"Date Modified: \" CONCAT FORMATDATETIME([modified],\"dddd, MMM d, yyyy\")"

  * FormatString also supports a full range of Python date/time formats.

JSON syntax

{
  "labelPlacement" : "<labelPlacement>",
  "labelExpression" : "<labelExpression>",
  "useCodedValues": <true | false>
  "symbol" : "<textSymbol>",
  "minScale" : <minScale>,
  "maxScale" : <maxScale>,
  "where" : "<where clause>"
}

JSON example

{
    "labelPlacement": "esriServerPointLabelPlacementAboveRight",
    "labelExpression": "[NAME]",
    "useCodedValues": false,
    "symbol": {
     "type": "esriTS",
     "color": [38,115,0,255],
     "backgroundColor": null,
     "borderLineColor": null,
     "verticalAlignment": "bottom",
     "horizontalAlignment": "left",
     "rightToLeft": false,
     "angle": 0,
     "xoffset": 0,
     "yoffset": 0,
     "kerning": true,
     "font": {
      "family": "Arial",
      "size": 11,
      "style": "normal",
      "weight": "bold",
      "decoration": "none"
     }
    },
    "minScale": 0,
    "maxScale": 0,
    "where" : "NAME LIKE 'A%'" //label only those feature where name begins with A
  }

Labeling info

The labeling info object specifies the label definition for a layer. It is expressed as an array of label classes.

JSON syntax

[ <labelClass1>, <labelClass2> ]

JSON example

[
   {
    "labelPlacement": "esriServerPolygonPlacementAlwaysHorizontal",
    "labelExpression": "[TAG]",
    "useCodedValues": false,
    "symbol": {
     "type": "esriTS",
     "color": [78,78,78,255],
     "backgroundColor": null,
     "borderLineColor": null,
     "verticalAlignment": "bottom",
     "horizontalAlignment": "left",
     "rightToLeft": false,
     "angle": 0,
     "xoffset": 0,
     "yoffset": 0,
     "font": {
      "family": "Arial",
      "size": 12,
      "style": "normal",
      "weight": "bold",
      "decoration": "none"
     }
    },
    "minScale": 1999,
    "maxScale": 0,
    "where": ""
   },
   {
    "labelPlacement": "esriServerPolygonPlacementAlwaysHorizontal",
    "labelExpression": "[TAG]",
    "useCodedValues": true,
    "symbol": {
     "type": "esriTS",
     "color": [78,78,78,255],
     "backgroundColor": null,
     "borderLineColor": null,
     "verticalAlignment": "bottom",
     "horizontalAlignment": "left",
     "rightToLeft": false,
     "angle": 0,
     "xoffset": 0,
     "yoffset": 0,
     "font": {
      "family": "Arial",
      "size": 12,
      "style": "normal",
      "weight": "bold",
      "decoration": "none"
     }
    },
    "minScale": 0,
    "maxScale": 7100,
    "where": ""
   }
  ]