c# - 在 C# 中调用 DrawRectangle 方法时如何使用 XOR 模式

Question

正如标题所说，我想用异或模式画一些东西，因为我想在一段时间后清理它。

我在 Visual Studio 2010 中使用 C#(窗口窗体)。

谁能帮我解决这个问题？

Answer 1

我为 .net 做了一个很好的扩展:

public static class XorDrawing
{

    [DllImport("gdi32.dll", EntryPoint = "SetROP2", CallingConvention = CallingConvention.StdCall)]
    private extern static int SetROP2(IntPtr hdc, int fnDrawMode);

    [DllImport("gdi32.dll", EntryPoint = "MoveToEx", CallingConvention = CallingConvention.StdCall)]
    private extern static bool MoveToEx(IntPtr hdc, int x, int y, IntPtr lpPoint);

    [DllImport("gdi32.dll", EntryPoint = "LineTo", CallingConvention = CallingConvention.StdCall)]
    private extern static bool LineTo(IntPtr hdc, int x, int y);

    [DllImport("gdi32.dll", SetLastError = true)]
    static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll", EntryPoint = "SelectObject")]
    public static extern IntPtr SelectObject([In] IntPtr hdc, [In] IntPtr hgdiobj);

    [DllImport("gdi32.dll")]
    static extern bool DeleteObject(IntPtr target);

    [DllImport("gdi32.dll")]
    static extern IntPtr CreatePen(PenStyle fnPenStyle, int nWidth, uint crColor);

    [DllImport("gdi32.dll")]
    static extern bool SetWorldTransform(IntPtr hdc, [In] ref XFORM lpXform);

    [DllImport("gdi32.dll")]
    public static extern int SetGraphicsMode(IntPtr hdc, int iMode);

    /// <summary>
    ///   The XFORM structure specifies a world-space to page-space transformation.
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
    public struct XFORM
    {
        public float eM11;
        public float eM12;
        public float eM21;
        public float eM22;
        public float eDx;
        public float eDy;

        public XFORM(float eM11, float eM12, float eM21, float eM22, float eDx, float eDy)
        {
            this.eM11 = eM11;
            this.eM12 = eM12;
            this.eM21 = eM21;
            this.eM22 = eM22;
            this.eDx = eDx;
            this.eDy = eDy;
        }

        /// <summary>
        ///   Allows implicit converstion to a managed transformation matrix.
        /// </summary>
        public static implicit operator System.Drawing.Drawing2D.Matrix(XFORM xf)
        {
            return new System.Drawing.Drawing2D.Matrix(xf.eM11, xf.eM12, xf.eM21, xf.eM22, xf.eDx, xf.eDy);
        }

        /// <summary>
        ///   Allows implicit converstion from a managed transformation matrix.
        /// </summary>
        public static implicit operator XFORM(System.Drawing.Drawing2D.Matrix m)
        {
            float[] elems = m.Elements;
            return new XFORM(elems[0], elems[1], elems[2], elems[3], elems[4], elems[5]);
        }
    }

    public enum BinaryRasterOperations
    {
        R2_BLACK = 1,
        R2_NOTMERGEPEN = 2,
        R2_MASKNOTPEN = 3,
        R2_NOTCOPYPEN = 4,
        R2_MASKPENNOT = 5,
        R2_NOT = 6,
        R2_XORPEN = 7,
        R2_NOTMASKPEN = 8,
        R2_MASKPEN = 9,
        R2_NOTXORPEN = 10,
        R2_NOP = 11,
        R2_MERGENOTPEN = 12,
        R2_COPYPEN = 13,
        R2_MERGEPENNOT = 14,
        R2_MERGEPEN = 15,
        R2_WHITE = 16
    }

    private enum PenStyle : int
    {
        PS_SOLID = 0, //The pen is solid.
        PS_DASH = 1, //The pen is dashed.
        PS_DOT = 2, //The pen is dotted.
        PS_DASHDOT = 3, //The pen has alternating dashes and dots.
        PS_DASHDOTDOT = 4, //The pen has alternating dashes and double dots.
        PS_NULL = 5, //The pen is invisible.
        PS_INSIDEFRAME = 6,// Normally when the edge is drawn, it’s centred on the outer edge meaning that half the width of the pen is drawn
        // outside the shape’s edge, half is inside the shape’s edge. When PS_INSIDEFRAME is specified the edge is drawn 
        //completely inside the outer edge of the shape.
        PS_USERSTYLE = 7,
        PS_ALTERNATE = 8,
        PS_STYLE_MASK = 0x0000000F,

        PS_ENDCAP_ROUND = 0x00000000,
        PS_ENDCAP_SQUARE = 0x00000100,
        PS_ENDCAP_FLAT = 0x00000200,
        PS_ENDCAP_MASK = 0x00000F00,

        PS_JOIN_ROUND = 0x00000000,
        PS_JOIN_BEVEL = 0x00001000,
        PS_JOIN_MITER = 0x00002000,
        PS_JOIN_MASK = 0x0000F000,

        PS_COSMETIC = 0x00000000,
        PS_GEOMETRIC = 0x00010000,
        PS_TYPE_MASK = 0x000F0000
    };

    public enum GraphicsMode : int
    {   
        GM_COMPATIBLE = 1,
        GM_ADVANCED = 2,
    }

    private static IntPtr BeginDraw(System.Drawing.Bitmap bmp, System.Drawing.Graphics graphics, int x1, int y1, int x2, int y2, bool dash, out int oldRop, out IntPtr img, out IntPtr oldpen)
    {
        var gHdc = graphics.GetHdc();
        var hdc = CreateCompatibleDC(gHdc);
        graphics.ReleaseHdc(hdc);

        img = bmp.GetHbitmap();
        SelectObject(hdc, img);

        oldpen = IntPtr.Zero;
        if (dash)
        {
            var pen = CreatePen(PenStyle.PS_DASH, 1, 0);
            oldpen = SelectObject(hdc, pen);
        }
        oldRop = SetROP2(hdc, (int)BinaryRasterOperations.R2_NOTXORPEN); // Switch to inverted mode. (XOR)

        SetGraphicsMode(hdc, (int)GraphicsMode.GM_ADVANCED);
        XFORM transform = graphics.Transform;
        SetWorldTransform(hdc, ref transform);

        return hdc;
    }


    private static void FinishDraw(System.Drawing.Bitmap bmp, System.Drawing.Graphics graphics, IntPtr hdc, IntPtr oldpen, int oldRop, IntPtr img, bool dash)
    {
        SetROP2(hdc, oldRop);

        var transform = graphics.Transform;
        graphics.ResetTransform(); //in case there is transform
        var outBmp = System.Drawing.Image.FromHbitmap(img);
        //CopyChannel(bmp, outBmp, ChannelARGB.Alpha, ChannelARGB.Alpha);
        graphics.Clear(Color.Transparent);
        graphics.DrawImage(outBmp, 0, 0); //draw the xored image on the bitmap
        graphics.Transform = transform;

        if (dash) DeleteObject(SelectObject(hdc, oldpen)); //delete new pen (switch to oldpen)
        DeleteObject(img); // Delete the GDI bitmap (important).
        DeleteObject(hdc);
    }

    public static void DrawXorLine(this System.Drawing.Graphics graphics, System.Drawing.Bitmap bmp, int x1, int y1, int x2, int y2, bool dash = true)
    {
        int oldRop;
        IntPtr oldpen, img;
        var hdc = BeginDraw(bmp, graphics, x1, y1, x2, y2, dash, out oldRop, out img, out oldpen);

        MoveToEx(hdc, x1, y1, IntPtr.Zero);
        LineTo(hdc, x2, y2);

        FinishDraw(bmp, graphics, hdc, oldpen, oldRop, img, dash);
    }

    public static void DrawXorRectangle(this System.Drawing.Graphics graphics, System.Drawing.Bitmap bmp, int x1, int y1, int x2, int y2, bool dash = true)
    {
        int oldRop;
        IntPtr oldpen, img;
        var hdc = BeginDraw(bmp, graphics, x1, y1, x2, y2, dash, out oldRop, out img, out oldpen);

        MoveToEx(hdc, x1, y1, IntPtr.Zero); //clockwise
        LineTo(hdc, x2, y1);
        LineTo(hdc, x2, y2);
        LineTo(hdc, x1, y2);
        LineTo(hdc, x1, y1);

        FinishDraw(bmp, graphics, hdc, oldpen, oldRop, img, dash);
    }
}

用法

g.DrawXorRectangle(bmp, outRect.Left, outRect.Top, outRect.Left + outRect.Width, outRect.Top + outRect.Height);

或者

g.DrawXorLine(bmp, x1, y1, x2, y2);