简单标签

简单标签指定了特征必须如何标记。

支持的选项有：

属性	描述
LabelAttribute	指定用作标签来源的属性名称。
LabelExpression	提供了一种自定义和格式化标签文本的方式。覆盖 LabelAttribute
FontFamily	指定用于渲染文本的字体系列。默认值取决于系统。
FontStyle	应用于文本的样式。 - FontStyle.Regular - 常规文本。 - FontStyle.Bold - 粗体文本。 - FontStyle.Italic - 斜体文本。 - FontStyle.Underine - 带下划线的文本。 - FontStyle.StrikeOut - 中间有一条线的文本。
FontSize	指定文本的大小。
FontColor	确定文本的颜色。
HaloSize	确定文本周围光晕（或轮廓）的大小。
HaloColor	确定文本周围光晕的颜色。
GeometryExpression	用于变换几何体的几何表达式，然后再将其传递给标签引擎。
MultipartMode	指定多部件几何体的渲染行为。 - MultipartMode.All - 在几何体的每个部分附近放置标签。 - MultipartMode.Any - 在几何体的任何一部分附近放置一个标签。 - MultipartMode.Largest - 在几何体的最大部分附近放置标签。
Placement	指定标签相对于几何体的位置方式。 - PointLabelPlacement - 将标签放置在几何体的中心附近。 - LineLabelPlacement - 将标签放置在线或其周长上。
Priority	指定标签的优先级，以防它与其他标签重叠。优先级较低的标签不会被渲染。默认值为 1000。

示例

点标签示例

默认情况下，SimpleLabeling 在点上绘制文本：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(500, 200))
	{
	var symbol = new SimpleMarker
	{
	FillColor = Color.LightGray,
	StrokeStyle = StrokeStyle.None
	};

	var labeling = new SimpleLabeling(labelAttribute: "name");

	map.Add(VectorLayer.Open(dataDir + "points.geojson", Drivers.GeoJson), symbol, labeling);
	map.Padding = 50;
	map.Render(dataDir + "points_labeling_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-PointsLabeling.cs hosted with ❤ by GitHub

以下是如何设置字体样式：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(500, 200))
	{
	var symbol = new SimpleMarker
	{
	FillColor = Color.LightGray,
	StrokeStyle = StrokeStyle.None
	};

	var labeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 2,
	HaloColor = Color.LightGray,
	FontSize = 15,
	FontStyle = FontStyle.Italic,
	};

	map.Add(VectorLayer.Open(dataDir + "points.geojson", Drivers.GeoJson), symbol, labeling);
	map.Padding = 50;
	map.Render(dataDir + "points_labeling_styled_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-PointsLabelingStyled.cs hosted with ❤ by GitHub

为了控制文本相对于点特征的位置，必须设置 placement 属性：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(500, 200))
	{
	var symbol = new SimpleMarker
	{
	FillColor = Color.LightGray,
	StrokeStyle = StrokeStyle.None
	};

	var labeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 1,
	Placement = new PointLabelPlacement
	{
	VerticalAnchorPoint = VerticalAnchor.Bottom,
	HorizontalAnchorPoint = HorizontalAnchor.Left,
	HorizontalOffset = 2,
	VerticalOffset = 2,
	Rotation = 10,
	}
	};

	map.Add(VectorLayer.Open(dataDir + "points.geojson", Drivers.GeoJson), symbol, labeling);
	map.Padding = 50;
	map.Render(dataDir + "points_labeling_placed_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-PointsLabelingPlaced.cs hosted with ❤ by GitHub

对于更高级的场景，您可能希望为特征选择不同的标签。以下是如何做到：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(500, 200))
	{
	var symbolizer = new SimpleMarker {FillColor = Color.LightGray, StrokeStyle = StrokeStyle.None};

	var labeling = new RuleBasedLabeling();
	// Set labeling to be used for small cities.
	labeling.Add(f => f.GetValue<int>("population") <= 2500, new SimpleLabeling("name")
	{
	FontStyle = FontStyle.Italic,
	HaloSize = 1,
	FontSize = 10,
	FontColor = Color.Green,
	Priority = 1,
	Placement = new PointLabelPlacement
	{
	VerticalAnchorPoint = VerticalAnchor.Bottom,
	HorizontalAnchorPoint = HorizontalAnchor.Center,
	}
	});
	// Set labeling to be used for all other cities.
	labeling.AddElseRule(new SimpleLabeling("name")
	{
	HaloSize = 1,
	FontSize = 15,
	FontColor = Color.Red,
	Priority = 2,
	Placement = new PointLabelPlacement
	{
	VerticalAnchorPoint = VerticalAnchor.Bottom,
	HorizontalAnchorPoint = HorizontalAnchor.Center,
	}
	});

	map.Add(VectorLayer.Open(dataDir + "points.geojson", Drivers.GeoJson), symbolizer, labeling);
	map.Padding = 40;
	map.Render(dataDir + "rule_based_labeling_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-RuleBasedLabeling.cs hosted with ❤ by GitHub

线标签示例

默认情况下，SimpleLabeling 在线的中心附近绘制标签：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(1000, 634))
	{
	var symbolizer = new SimpleLine { Width = 1.5, Color = Color.FromArgb(0xAE, 0xD9, 0xFD) };

	var labeling = new SimpleLabeling(labelAttribute: "name");

	map.Add(VectorLayer.Open(dataDir + "lines.geojson", Drivers.GeoJson), symbolizer, labeling);
	map.Padding = 50;
	map.Render(dataDir + "lines_labeling_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-LinesLabeling.cs hosted with ❤ by GitHub

为了使标签平行于线，可以使用 LineLabelPlacement 和 LineLabelAlignment.Parallel：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(1000, 634))
	{
	var symbolizer = new SimpleLine { Width = 1.5, Color = Color.FromArgb(0xAE, 0xD9, 0xFD) };

	var labeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 1,
	Placement = new LineLabelPlacement
	{
	Alignment = LineLabelAlignment.Parallel,
	}
	};

	map.Add(VectorLayer.Open(dataDir + "lines.geojson", Drivers.GeoJson), symbolizer, labeling);
	map.Padding = 50;
	map.Render(dataDir + "lines_labeling_parallel_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-LinesLabelingParallel.cs hosted with ❤ by GitHub

如果您希望文本精确地跟随线，可以使用 LineLabelPlacement 和 LineLabelAlignment.Curved：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(1000, 634))
	{
	var symbolizer = new SimpleLine { Width = 1.5, Color = Color.FromArgb(0xAE, 0xD9, 0xFD) };

	var labeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 1,
	Placement = new LineLabelPlacement
	{
	Alignment = LineLabelAlignment.Curved,
	}
	};

	map.Add(VectorLayer.Open(dataDir + "lines.geojson", Drivers.GeoJson), symbolizer, labeling);
	map.Padding = 50;
	map.Render(dataDir + "lines_labeling_curved_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-LinesLabelingCurved.cs hosted with ❤ by GitHub

如果您不希望文本与线重叠，请使用 LineLabelPlacement.Offset：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(1000, 634))
	{
	var symbolizer = new SimpleLine { Width = 1.5, Color = Color.FromArgb(0xAE, 0xD9, 0xFD) };

	var labeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 1,
	Placement = new LineLabelPlacement
	{
	Alignment = LineLabelAlignment.Curved,
	Offset = 5,
	}
	};

	map.Add(VectorLayer.Open(dataDir + "lines.geojson", Drivers.GeoJson), symbolizer, labeling);
	map.Padding = 50;
	map.Render(dataDir + "lines_labeling_curved_offset_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-LinesLabelingCurvedWithOffset.cs hosted with ❤ by GitHub

对于更高级的场景，您可能希望根据特征属性值动态调整标签样式。以下是如何做到：

	// For complete examples and data files, please go to https://github.com/aspose-gis/Aspose.GIS-for-.NET
	using (var map = new Map(1000, 634))
	{
	var lineSymbolizer = new SimpleLine { Width = 1.5, Color = Color.FromArgb(0xae, 0xd9, 0xfd) };
	lineSymbolizer.FeatureBasedConfiguration = (feature, symbolizer) =>
	{
	if (feature.GetValue<string>("NAM") == "UNK")
	{
	symbolizer.Width = 1;
	symbolizer.Style = StrokeStyle.Dash;
	}
	};


	var lineLabeling = new SimpleLabeling(labelAttribute: "name")
	{
	HaloSize = 1,
	Placement = new LineLabelPlacement
	{
	Alignment = LineLabelAlignment.Parallel,
	},
	FontSize = 20,
	FeatureBasedConfiguration = (feature, labeling) =>
	{
	if (feature.GetValue<string>("NAM") == "UNK")
	{
	// change labeling properties for some features.
	labeling.FontStyle = FontStyle.Italic;
	labeling.FontSize = 10;
	labeling.Priority = -1;

	var placement = (LineLabelPlacement) labeling.Placement;
	placement.Alignment = LineLabelAlignment.Curved;
	placement.Offset = 5;
	}
	}
	};

	map.Add(VectorLayer.Open(dataDir + "lines.geojson", Drivers.GeoJson), lineSymbolizer, lineLabeling);
	map.Padding = 50;
	map.Render(dataDir + "lines_labeling_feature_based_out.svg", Renderers.Svg);
	}

view raw Examples-CSharp-Rendering-LabelMap-LinesLabelingFeatureBased.cs hosted with ❤ by GitHub

基于规则的标签