Question

我正在研究尖锐地图，说我有美国地图，如何在地图上添加新图层？

因为我需要在基本层上写出状态的名称，并用不同的颜色为每个状态着色。是否有可能在Sharpmaps中实现这一目标......？

Answer 1

您必须为每个州使用“自定义”颜色，并为状态名称使用“标签层”

您必须先定义一个委托方法。委托将FeatureDataRow作为参数，您可以处理自定义样式

例如

private SharpMap.Styles.VectorStyle GetCountryStyle(SharpMap.Data.FeatureDataRow row)
{
    SharpMap.Styles.VectorStyle style = new SharpMap.Styles.VectorStyle();
    switch (row["NAME"].ToString().ToLower())
    {
        case "denmark": //If country name is Danmark, fill it with green
            style.Fill = Brushes.Green;
            return style;
        case "united states": //If country name is USA, fill it with Blue and add a red outline
            style.Fill = Brushes.Blue;
            style.Outline = Pens.Red;
            return style;
        case "china": //If country name is China, fill it with red
            style.Fill = Brushes.Red;
            return style;
        default:
            break;
    }
    //If country name starts with S make it yellow
    if (row["NAME"].ToString().StartsWith("S"))
    {
        style.Fill = Brushes.Yellow;
        return style;
    }
    // If geometry is a (multi)polygon and the area of the polygon is less than 30, make it cyan
    else if (row.Geometry is GeoAPI.Geometries.IPolygonal && row.Geometry.Area < 30)
    {
        style.Fill = Brushes.Cyan;
        return style;
    }
    else //None of the above -> Use the default style
        return null;
}

然后将图层的Theme属性设置为此方法

SharpMap.Rendering.Thematics.CustomTheme myTheme = new SharpMap.Rendering.Thematics.CustomTheme(GetCountryStyle);
myVectorLayer.Theme = myTheme ;

并且对于标签图层，您必须将新图层作为LabelLayer定义例如

//Name of table in database
string tablename = "Roads"; 
//Name of object ID column - MUST be integer!
string idColumn = "gid";

//Create layer
SharpMap.Layers.VectorLayer layRoads= new SharpMap.Layers.VectorLayer("Roads");
layRoads.DataSource = datasource;
//Set up a road label layer
SharpMap.Layers.LabelLayer layRoadLabel = new SharpMap.Layers.LabelLayer("Road labels");
//Set the datasource to that of layRoads.
layRoadLabel.DataSource = layRoads.DataSource;
layRoadLabel.Enabled = true;
//Specifiy field that contains the label string.
layRoadLabel.LabelColumn = "RoadOfName";

//Add layer to map
myMap.Layers.Add(layRoads);
//Add label layer to map
myMap.Layers.Add(layRoadLabel);

告诉所有here

Answer 2

我认为在锐界图中不可能。

但是，在c＃中，可以通过映射状态边界的坐标来实现。

在SHARPMAP中创建新图层

2 个答案: