Inheritance: UserBlendOp
		public void DarkenBlendOp2 ()
		{
			var lhs = GetSourceImage ("blend1.png");
			var rhs = GetSourceImage ("blend2.png");

			var lhs_wrap = new BitmapWrapper (lhs);
			var rhs_wrap = new BitmapWrapper (rhs);

			var op = new DarkenBlendOp ();
			op.Apply (rhs_wrap, lhs_wrap);

			Compare (lhs, "darkenblend2.png");
		}
		/// <summary>
		/// Creates a new effect that will make an image look like an ink sketch.
		/// </summary>
		/// <param name="inkOutline">Size of the ink outline. Valid range is 0 - 99.</param>
		/// <param name="coloring">Amount of color to keep. Valid range is 0 - 100.</param>
		public InkSketchEffect (int inkOutline = 50, int coloring = 50)
		{
			if (inkOutline < 0 || inkOutline > 99)
				throw new ArgumentOutOfRangeException ("inkOutline");
			if (coloring < 0 || coloring > 100)
				throw new ArgumentOutOfRangeException ("coloring");

			ink_outline = inkOutline;
			this.coloring = coloring;

			glow_effect = new GlowEffect (6, -(coloring - 50) * 2, -(coloring - 50) * 2);
			desaturate_op = new DesaturateOp ();
			darken_op = new DarkenBlendOp ();
		}