Constraining images with imageprocessor

Constrain.cs

using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text.RegularExpressions;
using ImageProcessor;
using ImageProcessor.Helpers.Extensions;
using ImageProcessor.Processors;
using ImageProcessor.Web.Config;

namespace Demo.ImageProcessors
{
  public class Constrain : IGraphicsProcessor
	{
		private static readonly Regex QueryRegex = new Regex(@"constrain=\d+,\d+", RegexOptions.Compiled);

		public Regex RegexPattern
		{
			get
			{
				return QueryRegex;
			}
		}


		public dynamic DynamicParameter { get; set; }
		public int SortOrder { get; private set; }
		public Dictionary<string, string> Settings { get; set; }

		public int MatchRegexIndex(string queryString)
		{
			int index = 0;

			// Set the sort order to max to allow filtering.
			this.SortOrder = int.MaxValue;

			foreach (Match match in this.RegexPattern.Matches(queryString))
			{
				if (match.Success)
				{
					if (index == 0)
					{
						// Set the index on the first instance only.
						this.SortOrder = match.Index;
						int[] constraints = match.Value.ToPositiveIntegerArray();

						int x = constraints[0];
						int y = constraints[1];

						this.DynamicParameter = new Size(x,y);
					}

					index += 1;
				}
			}

			return this.SortOrder;
		}

		public Image ProcessImage(ImageFactory factory)
		{

			double constrainedWidth = DynamicParameter.Width;
			double constrainedHeight = DynamicParameter.Height;
			
			var original = factory.Image;
			double width = original.Width;
			double height = original.Height;

			if (width > constrainedWidth || height > constrainedHeight)
			{

				double constraintRatio = constrainedHeight/constrainedWidth;
				double originalRatio = height/width;

				Size newSize = originalRatio < constraintRatio
					               ? new Size((int) constrainedWidth, 0)
					               : new Size(0, (int) constrainedHeight);

				var resizer = ImageProcessorConfig.Instance.GraphicsProcessors.FirstOrDefault(g => g is Resize) as Resize;

				if (resizer != null)
				{
					resizer.DynamicParameter = newSize;
					Image processed = resizer.ProcessImage(factory);
					return processed;
				}
			}
			return factory.Image;
		}
	}
}