Program.cs

using System;
using Emgu.CV;
using Emgu.CV.CvEnum;
using Emgu.CV.Structure;
using Emgu.CV.UI;
using System.Drawing;
using System.Runtime.InteropServices;

namespace cv
{
    public class SMat : Mat
    {
        protected long sizeInBytes;

        public void updateMemoryPressure()
        {
            var newSizeInBytes = Step * Rows;
            if (newSizeInBytes > sizeInBytes)
            {
                GC.AddMemoryPressure(newSizeInBytes - sizeInBytes);
            }
            else if (newSizeInBytes < sizeInBytes)
            {
                GC.RemoveMemoryPressure(sizeInBytes - newSizeInBytes);
            }
            sizeInBytes = newSizeInBytes;
        }

        public SMat(int rows, int cols, DepthType type, int channels) : base(rows, cols, type, channels)
        {
            sizeInBytes = Step * Rows;
            GC.AddMemoryPressure(sizeInBytes);
        }

        protected override void DisposeObject()
        {
            base.DisposeObject();
            if (_ptr == IntPtr.Zero)
            {
                GC.RemoveMemoryPressure(sizeInBytes);
            }
        }
    }
}
namespace emgu_ex1
{
    class Program
    {
        static void Main(string[] args)
        {
            //print_line("Hello, PInvoke!");
            //Create a 3 channel image of 400x200
            using (var img = new cv.SMat(400, 400, DepthType.Cv8U, 3))
            {
                img.SetTo(new Bgr(255, 0, 0).MCvScalar); // set it to Blue color

                img.updateMemoryPressure();

                //var ptr = img.DataPointer;
                set_color(img);

                ////Draw "Hello, world." on the image using the specific font
                //CvInvoke.PutText(
                //   img,
                //   "Hello, world",
                //   new System.Drawing.Point(10, 80),
                //   FontFace.HersheyComplex,
                //   1.0,
                //   new Bgr(0, 255, 0).MCvScalar);

                ////Show the image using ImageViewer from Emgu.CV.UI
                //ImageViewer.Show(img, "Test Window");
            }
            Console.WriteLine("here");
        }

        [DllImport("nativelib.dll")]
        private static extern void set_color(IntPtr data);
    }
}