New types/converters for markers and aspect ratio

Source/DataTypes/SvgAspectRatioConverter.cs

+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Svg.DataTypes
+{
+
+	//implementaton for preserve aspect ratio
+	public sealed class SvgPreserveAspectRatioConverter : TypeConverter
+	{
+		public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
+		{
+			if (value == null)
+			{
+				return new SvgAspectRatio();
+			}
+
+			if (!(value is string))
+			{
+				throw new ArgumentOutOfRangeException("value must be a string.");
+			}
+
+			SvgPreserveAspectRatio eAlign = SvgPreserveAspectRatio.none;
+			if (!Enum.TryParse<SvgPreserveAspectRatio>(value as string, out eAlign))
+				throw new ArgumentOutOfRangeException("value is not a member of SvgPreserveAspectRatio");
+
+			SvgAspectRatio pRet = new SvgAspectRatio(eAlign);
+			return (pRet);
+		}
+
+		public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+		{
+			if (sourceType == typeof(string))
+			{
+				return true;
+			}
+
+			return base.CanConvertFrom(context, sourceType);
+		}
+
+		public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
+		{
+			if (destinationType == typeof(string))
+			{
+				return true;
+			}
+
+			return base.CanConvertTo(context, destinationType);
+		}
+
+		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
+		{
+			if (destinationType == typeof(string))
+			{
+				return ((SvgUnit)value).ToString();
+			}
+
+			return base.ConvertTo(context, culture, value, destinationType);
+		}
+	}
+}

Source/DataTypes/SvgMarkerUnits.cs

+using System.ComponentModel;
+
+namespace Svg.DataTypes
+{
+	[TypeConverter(typeof(SvgMarkerUnitsConverter))]
+	public enum SvgMarkerUnits
+	{
+		strokeWidth,
+		userSpaceOnUse
+	}
+}

Source/DataTypes/SvgOrientConverter.cs

+using System;
+using System.ComponentModel;
+using System.Globalization;
+
+namespace Svg.DataTypes
+{
+	public sealed class SvgOrientConverter : TypeConverter
+	{
+		public override object ConvertFrom(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value)
+		{
+			if (value == null)
+			{
+				return new SvgUnit(SvgUnitType.User, 0.0f);
+			}
+
+			if (!(value is string))
+			{
+				throw new ArgumentOutOfRangeException("value must be a string.");
+			}
+
+			switch (value.ToString())
+			{
+				case "auto":
+					return (new SvgOrient());
+				default:
+					float fTmp = float.MinValue;
+					if(!float.TryParse(value.ToString(), out fTmp))
+						throw new ArgumentOutOfRangeException("value must be a valid float.");
+					return (new SvgOrient(fTmp));
+			}
+		}
+
+		public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+		{
+			if (sourceType == typeof(string))
+			{
+				return true;
+			}
+
+			return base.CanConvertFrom(context, sourceType);
+		}
+
+		public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
+		{
+			if (destinationType == typeof(string))
+			{
+				return true;
+			}
+
+			return base.CanConvertTo(context, destinationType);
+		}
+
+		public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
+		{
+			if (destinationType == typeof(string))
+			{
+				return ((SvgUnit)value).ToString();
+			}
+
+			return base.ConvertTo(context, culture, value, destinationType);
+		}
+	}
+}