anjianjingling/Forms/OverlayForm.cs

using anjianjingling.Native;

namespace anjianjingling.Forms
{
    /// <summary>
    /// 全屏框选截图：鼠标拖拽框选区域，松开后截图保存到 images 目录。
    /// ESC 取消。
    /// </summary>
    public sealed class OverlayForm : Form
    {
        private Point _start, _end;
        private bool _dragging;
        private Rectangle _selected;
        public string? SavedPath { get; private set; }
        public event Action<string>? OnSaved;

        /// <summary>是否把框选结果保存为图片（录屏取区域时设为 false）。</summary>
        [System.ComponentModel.Browsable(false)]
        [System.ComponentModel.DesignerSerializationVisibility(System.ComponentModel.DesignerSerializationVisibility.Hidden)]
        public bool SaveToFile { get; set; } = true;

        /// <summary>最近一次框选的屏幕矩形。</summary>
        [System.ComponentModel.Browsable(false)]
        [System.ComponentModel.DesignerSerializationVisibility(System.ComponentModel.DesignerSerializationVisibility.Hidden)]
        public Rectangle SelectedRect { get; private set; }

        public OverlayForm()
        {
            FormBorderStyle = FormBorderStyle.None;
            StartPosition = FormStartPosition.Manual;
            Bounds = SystemInformation.VirtualScreen;
            TopMost = true;
            ShowInTaskbar = false;
            DoubleBuffered = true;
            KeyPreview = true;
            BackColor = Color.Black;
            Opacity = 0.25;
            Cursor = Cursors.Cross;

            MouseDown += (s, e) =>
            {
                if (e.Button == MouseButtons.Left)
                {
                    _dragging = true;
                    _start = _end = PointToScreen(e.Location);
                }
            };
            MouseMove += (s, e) =>
            {
                if (_dragging)
                {
                    _end = PointToScreen(e.Location);
                    var r = RectangleFromPoints(_start, _end);
                    _selected = r;
                    Invalidate();
                }
            };
            MouseUp += (s, e) =>
            {
                if (_dragging && e.Button == MouseButtons.Left)
                {
                    _dragging = false;
                    var r = RectangleFromPoints(_start, _end);
                    if (r.Width > 4 && r.Height > 4)
                    {
                        SelectedRect = r;
                        if (SaveToFile)
                        {
                            string dir = Path.Combine(AppContext.BaseDirectory, "images");
                            Directory.CreateDirectory(dir);
                            string file = Path.Combine(dir,
                                $"clip_{DateTime.Now:yyyyMMdd_HHmmss}.png");
                            using (var bmp = new Bitmap(r.Width, r.Height))
                            using (var g = Graphics.FromImage(bmp))
                            {
                                g.CopyFromScreen(r.Left, r.Top, 0, 0, r.Size);
                                bmp.Save(file, System.Drawing.Imaging.ImageFormat.Png);
                            }
                            SavedPath = file;
                            OnSaved?.Invoke(file);
                        }
                        DialogResult = DialogResult.OK;
                        Close();
                        return;
                    }
                    Invalidate();
                }
            };
            KeyDown += (s, e) =>
            {
                if (e.KeyCode == Keys.Escape)
                {
                    DialogResult = DialogResult.Cancel;
                    Close();
                }
            };
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            if (_selected.Width > 0)
            {
                // 用屏幕坐标转客户区绘制
                var r = ScreenRectToClient(_selected);
                using (var pen = new Pen(Color.Lime, 1))
                {
                    e.Graphics.DrawRectangle(pen, r);
                    string info = $"{_selected.Width} x {_selected.Height}  ({_selected.Left},{_selected.Top})";
                    using var font = new Font("Consolas", 9F);
                    var sz = e.Graphics.MeasureString(info, font);
                    float ty = r.Top - sz.Height - 2;
                    if (ty < 0) ty = r.Bottom + 2;
                    using var bg = new SolidBrush(Color.Lime);
                    e.Graphics.FillRectangle(bg, r.Left, ty, sz.Width, sz.Height);
                    e.Graphics.DrawString(info, font, Brushes.Black, r.Left, ty);
                }
            }
        }

        private static Rectangle RectangleFromPoints(Point a, Point b)
            => Rectangle.FromLTRB(
                Math.Min(a.X, b.X), Math.Min(a.Y, b.Y),
                Math.Max(a.X, b.X), Math.Max(a.Y, b.Y));

        private Rectangle ScreenRectToClient(Rectangle screen)
        {
            var a = PointToClient(new Point(screen.Left, screen.Top));
            var b = PointToClient(new Point(screen.Right, screen.Bottom));
            return new Rectangle(a.X, a.Y, b.X - a.X, b.Y - a.Y);
        }
    }
}