我正在处理锐化 map ,假设我有一张美国 map ,如何在 map 上添加新图层?
因为我需要在基本层上写下状态的名称,并用不同的颜色为每个状态着色。 是否有可能在 Sharpmaps 中实现这个目标...?
最佳答案
您必须为每个州使用“自定义它们”颜色,为州名称使用“标签层”
您必须首先定义一个委托(delegate)方法。该委托(delegate)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 ;
对于标签图层,您必须按照 LabelLayer 定义的方式新建图层 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
关于c# - 在 SHARPMAP 中创建新图层,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9595681/