using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication19
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Bitmap vzor = (Bitmap)pictureBox1.Image;
            Bitmap kopie = new Bitmap(vzor.Width, vzor.Height);
            pictureBox2.Image = kopie;

            int[] zbytek = new int[vzor.Height];
            int[] budouci_zbytek = new int[vzor.Height];



            for (int x = 0; x < pictureBox1.Width; x++)
            {
                zbytek = budouci_zbytek;
                budouci_zbytek = new int[vzor.Height];

                for (int y = 0; y < pictureBox1.Height; y++)
                {

                    //int xx = pictureBox1.Width - 1 - x;
                    int xx = x;
                    if (2 * x < vzor.Width)
                        xx = 2 * x;
                    int yy = y;
                    if (2 * y < vzor.Height)
                        yy = 2 * y;

                    xx = x + 20+(int)(20 * Math.Sin(y / 30.00));
                    yy = y + 20+(int)(20 * Math.Sin(x / 30.00));



                    Color c = vzor.GetPixel(xx, yy);
                    int svetlost = (int)(c.R * 0.2989 + c.G * 0.5866 + c.B * (1 - 0.2989 - 0.5866));
                    svetlost += zbytek[y];

                    Color barva = c;
                    /*
                    if (svetlost >= trackBar1.Value)
                    {
                        barva = Color.White;
                        svetlost = svetlost - trackBar1.Value;
                    }
                    else barva = Color.Black;

                    kopie.SetPixel(x, y, barva);

                    if (y+1 < vzor.Height)
                        zbytek[y + 1] += svetlost / 4;
                    if (y-1 >=0)
                        budouci_zbytek[y - 1] += svetlost / 4;
                    budouci_zbytek[y] += svetlost / 4;
                    if (y + 1 < vzor.Height)
                        budouci_zbytek[y + 1] += svetlost / 4;
                     * */

                    //barva = Color.FromArgb(255, 255 - c.R, 255 - c.G, 255 - c.B);


                    kopie.SetPixel(x, y, barva);
                }
                Refresh();
            }
        }

        private void trackBar1_Scroll(object sender, EventArgs e)
        {
            button1_Click(null, null);
        }

        int LHRx = 0;
        int LHRy = 0;

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            LHRx = e.X;
            LHRy = e.Y;
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            Bitmap vzor = (Bitmap)pictureBox1.Image;
            Bitmap kopie = new Bitmap(vzor.Width, vzor.Height);
            pictureBox2.Image = kopie;
            
            int PDRx = e.X;
            int PDRy = e.Y;

            Graphics g = Graphics.FromImage(kopie);


            Rectangle R = new Rectangle(LHRx,LHRy,(PDRx-LHRx),(PDRy-LHRy));
            g.DrawImage(
                vzor.Clone(R,System.Drawing.Imaging.PixelFormat.DontCare),
                100,100 );
                

        }
    }
}

--------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication18
{
    public partial class Form1 : Form
    {

        Bitmap bmp;
        Graphics g;

        public Form1()
        {
            InitializeComponent();
            bmp = new Bitmap(1000, 1000);
            g = Graphics.FromImage(bmp);
            pictureBox1.Image = bmp;

        }

        private void button1_Click_2(object sender, EventArgs e)
        {
            //Graphics g = CreateGraphics();

            int sx = ClientRectangle.Width / 16;
            int sy = ClientRectangle.Height / 16;

            for (int i = 0; i < 16; i++)
            {
                for (int j = 0; j < 16; j++)
                {
                    int x = i * sx;
                    int y = j * sy;

                    Color barva = Color.FromArgb(255, j * 17, 17 * i, trackBar1.Value);
                    Brush stetec = new SolidBrush(barva);

                    g.FillRectangle(stetec, x, y, sx, sy);
                    g.DrawRectangle(Pens.Black, x, y, sx, sy);

                }

            }
            Refresh();
            
        }



        private void button1_Click(object sender, EventArgs e)
        {
            //Graphics g = CreateGraphics();
            g.DrawLine(Pens.Blue, 0, 0, 500, 500);
        }
        
        
        private void button1_Click_1(object sender, EventArgs e)
        {
            Graphics g = CreateGraphics();
            g.DrawLine(Pens.Blue, 0, 0, 100, 100);

            int minx = 0;
            int miny = 0;
            Pen pero = new Pen(Color.Red, 100);
            pero.StartCap 
                = System.Drawing.Drawing2D.LineCap.Round;
            pero.EndCap = System.Drawing.Drawing2D.LineCap.Round;
            for (int fi = 0; fi < 4*360; fi++)
            {
                int x = 250 + (int)(200 * Math.Cos(3 * (double)fi / 3/360.00 * 2 * Math.PI));
                int y = 250 + (int)(200 * Math.Sin(4 * (double)fi / 3 / 360.00 * 2 * Math.PI));

                pero.Width = 5;
                //pero.Color = Color.

                //if (fi > 0)
                //    g.DrawLine(pero, minx, miny, x, y);
                minx = x;
                miny = y;

                g.FillRectangle(Brushes.Yellow, x, y, 50, trackBar1.Value);
                g.DrawRectangle(Pens.Black, x, y, 50, 30);



            }


        }

        private void trackBar1_Scroll(object sender, EventArgs e)
        {
            button1_Click_2(null, null);

        }
    }
}