Overview
This topic discusses the JSON labeling objects as returned by the REST API.
The following objects are discussed:
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:
* FormatString also supports a full range of Python date/time formats.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\")"
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": ""
}
]