Add new Draw() method that can take raster size and render image in that given size

Source/SvgDocument.cs

@@ -490,6 +490,61 @@ namespace Svg
             //Trace.TraceInformation("End Render");
         }
 
+        /// <summary>
+        /// Renders the <see cref="SvgDocument"/> in given size and returns the image as a <see cref="Bitmap"/>.
+        /// </summary>
+        /// <returns>A <see cref="Bitmap"/> containing the rendered document.</returns>
+        public virtual Bitmap Draw(int rasterWidth, int rasterHeight)
+        {
+          var size = GetDimensions();
+          RasterizeDimensions(ref size, rasterWidth, rasterHeight);
+
+          if (size.Width == 0 || size.Height == 0)
+            return null;
+
+          var bitmap = new Bitmap((int)Math.Round(size.Width), (int)Math.Round(size.Height));
+          try
+          {
+            Draw(bitmap);
+          }
+          catch
+          {
+            bitmap.Dispose();
+            throw;
+          }
+
+          //Trace.TraceInformation("End Render");
+          return bitmap;
+        }
+
+        /// <summary>
+        /// If both or one of raster height and width is not given (0), calculate that missing value from original SVG size
+        /// while keeping original SVG size ratio
+        /// </summary>
+        /// <param name="size"></param>
+        /// <param name="rasterWidth"></param>
+        /// <param name="rasterHeight"></param>
+        public virtual void RasterizeDimensions(ref SizeF size, int rasterWidth, int rasterHeight)
+        {
+          if (size == null || size.Width == 0)
+            return;
+
+          // Ratio of height/width of the original SVG size, to be used for scaling transformation
+          float ratio = size.Height / size.Width;
+
+          size.Width = rasterWidth > 0 ? (float)rasterWidth : size.Width;
+          size.Height = rasterHeight > 0 ? (float)rasterHeight : size.Height;
+
+          if (rasterHeight == 0 && rasterWidth > 0)
+          {
+            size.Height = (int)(rasterWidth * ratio);
+          }
+          else if (rasterHeight > 0 && rasterWidth == 0)
+          {
+            size.Width = (int)(rasterHeight / ratio);
+          }
+        }
+
         public override void Write(XmlTextWriter writer)
         {
             //Save previous culture and switch to invariant for writing