Write state name on svg map using jqv map

问题

I have created USA states map using jqvmap . See jqvmap.com

I want to write state names in middle of map like image below.

I have tried using pseudo elements but its not working.

This is my code.

jQuery(document).ready(function () {
                jQuery('#vmap').vectorMap({
                    map: 'usa_en',
                    enableZoom: false,
                    showTooltip: true,
                    backgroundColor: '#D9D9D9',
                    color: '#009F45',
                    borderColor: '#ffffff',
                    borderOpacity: 0.25,
                    borderWidth: 2,
                    hoverColor: '#999999',
                    selectedColor: '#0077aa',
                    selectedRegion: 'MO',
                    onRegionClick: function (element, code, region)
                    {
                        var message = 'You clicked "'
                                + region
                                + '" which has the code: '
                                + code.toUpperCase();
                        alert(message);
                    }

                });

            });

/*!
 * jQVMap Version 1.0 
 *
 * http://jqvmap.com
 *
 * Copyright 2012, Peter Schmalfeldt <manifestinteractive@gmail.com>
 * Licensed under the MIT license.
 *
 * Fork Me @ https://github.com/manifestinteractive/jqvmap
 */
.jqvmap-label
{
    position: absolute;
    display: none;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
    background: #292929;
    color: white;
    font-family: sans-serif, Verdana;
    font-size: smaller;
    padding: 3px;
}
.jqvmap-zoomin, .jqvmap-zoomout
{
    position: absolute;
    left: 10px;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
    background: #000000;
    padding: 3px;
    color: white;
    width: 10px;
    height: 10px;
    cursor: pointer;
    line-height: 10px;
    text-align: center;
}
.jqvmap-zoomin
{
    top: 10px;
}
.jqvmap-zoomout
{
    top: 30px;
}
.jqvmap-region
{
    cursor: pointer;
}
.jqvmap-ajax_response
{
    width: 100%;
    height: 500px;
}

/*Colors of state*/

path#jqvmap1_nj{
    fill:#7AC37A;
}

path#jqvmap1_tn{
    fill:#7AC37A;
}

path#jqvmap1_in{
    fill:#7AC37A;
}

path#jqvmap1_co{
    fill:#7AC37A;
}

path#jqvmap1_ca{
    fill:#026E38;
}
path#jqvmap1_ca:after{
    content:'ca';
    position: absolute;
    top: 0;
    color:#fff;
}

path#jqvmap1_ak{
    fill:#6E6F73;
}

path#jqvmap1_tx{
    fill:#6E6F73;
}

path#jqvmap1_ar{
    fill:#6E6F73;
}

path#jqvmap1_la{
    fill:#6E6F73;
}

path#jqvmap1_al{
    fill:#6E6F73;
}

path#jqvmap1_nh{
    fill:#6E6F73;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<script src="https://jqvmap.com/js/vmap/jquery.vmap.js"></script>
<script src="https://jqvmap.com/js/vmap/jquery.vmap.usa.js"></script>
<div id="vmap" style="width: 600px; height: 400px;"></div>

回答1:

First, there is no built-in parameter in jqvmap to add the states code.

Finding a good position for this labels is not a trivial task. For example, Florida's shape is not convex, Michigan has two parts.

Some questions related on stackexchange network:
- Algorithm for finding irrregular polygon centroid (label point)
- How to split compound polygons into convex polygons?
- Partitioning a polygon into convex parts

So, I tried to place them with a dummy algorithm, which places the state code at a kind of centroid of state shapes. Then, you can move them as you want, and use the positions you have set.

Here is the main function which compute the centroid of a SVG path:

     //svgPathParser => browserified version of
     // https://github.com/hughsk/svg-path-parser
     var parsedPath= svgPathParser(path);

    // pathes in jqvmap are, for the most of them, in the form of [ start Point, [ curves ] ]
    // if you want better results it is possible to refine that.
    var origin= { x: parsedPath[0].x, y: parsedPath[0].y };
    var pathPartCentroids= [];
    var totalLength= 0;
    for( var i=1; i< parsedPath.length - 1; i++){

        var pathPart= parsedPath[i];

        if(pathPart.code !="c")
            break;

        //centroidOfPathPart returns the centroid of a Bezier curve. 
        var pathPartCentroid= centroidOfPathPart([ [0,0], [ pathPart.x1, pathPart.y1 ], [ pathPart.x2, pathPart.y2 ], [ pathPart.x, pathPart.y ] ]); 

        pathPartCentroid.x += origin.x;
        pathPartCentroid.y += origin.y;

        pathPartCentroid={ centroid: pathPartCentroid, distance: norm( pathPartCentroid, origin) } 
        pathPartCentroids.push(pathPartCentroid);

        totalLength+= pathPartCentroid.distance;

        origin.x+= pathPart.x;
        origin.y+= pathPart.y;
    }

    var centroid= {x:0,y:0};

    //segments are weighted by their length 
    pathPartCentroids.forEach(function( pathPart ){
        centroid.x += pathPart.centroid.x * pathPart.distance / totalLength;
        centroid.y += pathPart.centroid.y * pathPart.distance / totalLength;
    });

You can edit position with this pen.
Then use that another one to add state codes in a map.

来源：https://stackoverflow.com/questions/29966067/write-state-name-on-svg-map-using-jqv-map