kev/Drawer/ColorPicker/FrmPicker.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace GeoSigma
{
    public partial class FrmPicker : Form
    {
        PictureBox pictureBox;
        Bitmap bmp;
        Graphics g;
        bool isDown = false;
        Point downPoint;

        Rectangle rect;
        Pen pen;
        Bitmap bmpZoom;
        Graphics zoom;
        int zoomSize = 0;
        Color selectedColor = Color.White;
        public Color SelectedColor
        {
            get { return selectedColor; }
            set { selectedColor = value; }
        }
        public FrmPicker()
        {
            InitializeComponent();

            pictureBox = new PictureBox();
            pictureBox.Dock = DockStyle.Fill;
            pictureBox.BorderStyle = BorderStyle.None;
            pictureBox.MouseUp += new MouseEventHandler(pictureBox_MouseUp);
            pictureBox.MouseMove += new MouseEventHandler(pictureBox_MouseMove);
            pictureBox.Cursor = Cursors.Cross;

            this.Controls.Add(pictureBox);
            this.Size = new Size(0, 0);
            this.DoubleBuffered = true;

            bmpZoom = new Bitmap(picZoom.Width, picZoom.Height);
            zoom = Graphics.FromImage(bmpZoom);
            picZoom.Image?.Dispose();
            picZoom.Image = bmpZoom;

            pen = new Pen(Color.Black, 1);
            pen.DashCap = DashCap.Round;
            pen.DashStyle = DashStyle.Dash;

            zoomSize = tckZoomSize.Value;

            pictureBox.PreviewKeyDown += PictureBox_PreviewKeyDown;
        }

        private void PictureBox_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
        {
            //throw new NotImplementedException();
        }

        private void FrmPicker_Load(object sender, EventArgs e)
        {
            rect = new Rectangle(0, 0, 0, 0);
            //Screen[] scrs = Screen.AllScreens;

            //for(int i = 0; i < scrs.Length; i++)
            //{
            //    Rectangle recCur = scrs[i].Bounds;
            //    if (recCur.Right > rect.Right)
            //    {
            //        rect.Width += (recCur.Right- rect.Right);
            //    }
            //    if(recCur.Bottom> rect.Bottom)
            //    {
            //        rect.Height += (recCur.Bottom - rect.Bottom);
            //    }
            //}

            RefreshActualScreens();
            foreach(MonitorInfo screen in ActualScreens)
            {
                Rectangle recCur = screen.Bounds;
                if (recCur.Right > rect.Right)
                {
                    rect.Width += (recCur.Right - rect.Right);
                }
                if (recCur.Bottom > rect.Bottom)
                {
                    rect.Height += (recCur.Bottom - rect.Bottom);
                }
            }

            bmp = new Bitmap(rect.Width, rect.Height);

            g = Graphics.FromImage(bmp);
            g.CopyFromScreen(0, 0, 0, 0, rect.Size);
            pictureBox.Image?.Dispose();
            pictureBox.Image = bmp;            

            this.TopMost = true;
            this.FormBorderStyle = FormBorderStyle.None;
            this.WindowState = FormWindowState.Normal;
            this.Bounds = rect;
            //Point pt = this.PointToScreen(this.Owner.Location);
            //MessageBox.Show(this.Owner.Location.ToString() + "\r\n" + pt.ToString());
        }
        void pictureBox_MouseMove(object sender, MouseEventArgs e)
        {
            Point mousePoint = Control.MousePosition;
            lblXValue.Text = mousePoint.X.ToString();
            lblYValue.Text = mousePoint.Y.ToString();

            Color color = bmp.GetPixel(mousePoint.X, mousePoint.Y);
            lblShowColor.BackColor = color;
            txtColorValue.Text = string.Format("{0:d},{1:d},{2:d}"
                , color.R
                , color.G
                , color.B);

            zoom.InterpolationMode = InterpolationMode.NearestNeighbor;
            zoom.DrawImage(bmp, new Rectangle(0, 0, bmpZoom.Width, bmpZoom.Height),
                Control.MousePosition.X - bmpZoom.Width / (2 * zoomSize),
                Control.MousePosition.Y - bmpZoom.Height / (2 * zoomSize),
                bmpZoom.Width / zoomSize, bmpZoom.Height / zoomSize,
                GraphicsUnit.Pixel);
            zoom.DrawLine(pen, picZoom.Width / 2 - 1, 0, picZoom.Width / 2 - 1, picZoom.Height);
            zoom.DrawLine(pen, 0, picZoom.Height / 2 - 1, picZoom.Width, picZoom.Height / 2 - 1);

            picZoom.Refresh();
        }

        void pictureBox_MouseUp(object sender, MouseEventArgs e)
        {
            if(e.Button != MouseButtons.Left)
            {
                CancelForm();
                return;
            }
            selectedColor = bmp.GetPixel(e.Location.X, e.Location.Y);

            pen.Dispose();
            bmp.Dispose();
            bmpZoom.Dispose();
            zoom.Dispose();
            g.Dispose();
            this.DialogResult = DialogResult.OK;
            Close();
        }
        private void CancelForm()
        {
            this.DialogResult = DialogResult.Cancel;
            pen.Dispose();
            bmp.Dispose();
            bmpZoom.Dispose();
            zoom.Dispose();
            g.Dispose();

            this.Close();
        }
        private void pnlColorWindow_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isDown = true;
                downPoint = e.Location;
            }
        }

        private void pnlColorWindow_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDown)
            {
                pnlColorWindow.Left = Control.MousePosition.X - downPoint.X;
                pnlColorWindow.Top = Control.MousePosition.Y - downPoint.Y;
            }
        }

        private void pnlColorWindow_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                isDown = false;
            }
        }
        private void tckZoomSize_ValueChanged(object sender, EventArgs e)
        {
            zoomSize = tckZoomSize.Value;
        }

        private void FrmPicker_KeyPress(object sender, KeyPressEventArgs e)
        {
            if(e.KeyChar == (char)Keys.Escape)
            {
                CancelForm();
            }
        }

        public static List<MonitorInfo> ActualScreens = new List<MonitorInfo>();
        public static void RefreshActualScreens()
        {
            ActualScreens.Clear();
            MonitorEnumProc callback = (IntPtr hDesktop, IntPtr hdc, ref Rect prect, int d) =>
            {
                ActualScreens.Add(new MonitorInfo()
                {
                    Bounds = new Rectangle()
                    {
                        X = prect.left,
                        Y = prect.top,
                        Width = prect.right - prect.left,
                        Height = prect.bottom - prect.top,
                    },
                    IsPrimary = (prect.left == 0) && (prect.top == 0),
                });

                return true;
            };

            EnumDisplayMonitors(IntPtr.Zero, IntPtr.Zero, callback, 0);
        }

        [DllImport("user32")]
        private static extern bool EnumDisplayMonitors(IntPtr hdc, IntPtr lpRect, MonitorEnumProc callback, int dwData);

        private delegate bool MonitorEnumProc(IntPtr hDesktop, IntPtr hdc, ref Rect pRect, int dwData);

        [StructLayout(LayoutKind.Sequential)]
        private struct Rect
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }
    }
    public class MonitorInfo
    {
        public bool IsPrimary = false;
        public Rectangle Bounds = new Rectangle();
    }
}