ArcEngine实现要素图层唯一值符号化（渲染）（20190909）
1、需求
选择地图中某一要素图层的属性，对其进行唯一值符号化（相同的属性用同样的颜色渲染）
2、解决方案
（1）IUniqueValueRenderer接口实现要素唯一值的渲染；
（2）IRandomColorRamp接口创建随机颜色带；
3、界面设计
主要有两个界面，分别是主窗体界面和唯一值符号化界面
（1）主界面：
（2）唯一值符号化界面
4、代码实现
实现要素图层属性唯一值设色的方法，这里一定要注意COM对象的手动释放（包括其他任何情况下IQueryFiter、ICursour都必须手动释放，否则容易造成内存溢出）
///
/// 实现要素图层属性唯一值设色
///
/// 需要设色的要素图层
/// 唯一值的属性字段
private void UniqueValueRenderer(IFeatureLayer pFeatureLayer, string fieldName)
{
IGeoFeatureLayer pGeoFeatureLayer = pFeatureLayer as IGeoFeatureLayer;
ITable pTable = pFeatureLayer as ITable;
int fieldNumber = pTable.FindField(fieldName);
IUniqueValueRenderer pUniqueRenderer = new UniqueValueRendererClass();
pUniqueRenderer.FieldCount = 1;
pUniqueRenderer.set_Field(0, fieldName);
//设置显示颜色的范围
IRandomColorRamp pRandColorRamp = new RandomColorRampClass();
pRandColorRamp.StartHue = 0;
pRandColorRamp.MinValue = 85;
pRandColorRamp.MinSaturation = 15;
pRandColorRamp.EndHue = 360;
pRandColorRamp.MaxValue = 100;
pRandColorRamp.MaxSaturation = 30;
//创建随机颜色带
pRandColorRamp.Size = getUniqueValue(pFeatureLayer.FeatureClass, fieldName).Count;
bool bSucess = false;
pRandColorRamp.CreateRamp(out bSucess);
IEnumColors pEnumColors = pRandColorRamp.Colors;
IColor pNextUniqueColor = null;
//属性唯一值
IQueryFilter pQueryFilter = new QueryFilterClass();
pQueryFilter.AddField(fieldName);
ICursor pCursor = pFeatureLayer.FeatureClass.Search(pQueryFilter, false) as ICursor;
IRow pNextRow = pCursor.NextRow();
object codeValue = null;
IRowBuffer pNextRowBuffer = null;
IFillSymbol pFillSymbol = null;
ILineSymbol pLineSymbol = null;
IMarkerSymbol pMarkerSymbol = null;
while (pNextRow != null)
{
pNextRowBuffer = pNextRow as IRowBuffer;
codeValue = pNextRowBuffer.get_Value(fieldNumber);
pNextUniqueColor = pEnumColors.Next();
if (pNextUniqueColor == null)
{
pEnumColors.Reset();
pNextUniqueColor = pEnumColors.Next();
}
switch (pGeoFeatureLayer.FeatureClass.ShapeType)
{
case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPoint:
pMarkerSymbol = new SimpleMarkerSymbolClass();
pMarkerSymbol.Color = pNextUniqueColor;
pUniqueRenderer.AddValue(codeValue.ToString(), "", pMarkerSymbol as ISymbol);
pNextRow = pCursor.NextRow();
break;
case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolyline:
pLineSymbol = new SimpleLineSymbolClass();
pLineSymbol.Color = pNextUniqueColor;
pUniqueRenderer.AddValue(codeValue.ToString(), "", pLineSymbol as ISymbol);
pNextRow = pCursor.NextRow();
break;
case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolygon:
pFillSymbol = new SimpleFillSymbolClass();
pFillSymbol.Color = pNextUniqueColor;
pUniqueRenderer.AddValue(codeValue.ToString(), "", pFillSymbol as ISymbol);
pNextRow = pCursor.NextRow();
int k = pFillSymbol.Color.CMYK;
break;
default:
break;
}
}
pGeoFeatureLayer.Renderer = pUniqueRenderer as IFeatureRenderer;
//必须手动清除COM对象，否则会造成内存溢出（尤其是IQueryFilter,ICursor）
Marshal.ReleaseComObject(pQueryFilter);
Marshal.ReleaseComObject(pCursor);
Marshal.ReleaseComObject(pEnumColors);
}
5、代码下载
github: ArcEngine实现要素图层唯一值符号化