DotNet实现PictureBox重叠透明效果

　　本文介绍DotNet中PictureBox控件实现重叠透明效果示例。

　　关于一般的透明效果，这里不多说，相信很多人都会，这种透明效果一般需要设置父控件，是子控件相对于父控件的透明。那么很多人可能更为关心的是多个控件之间的透明效果，比如窗体上有多个PictureBox控件，当这些PictureBox重叠时如何设置为透明，这样的效果估计在项目中会经常用到。本文的目的就是要给大家提供几种参考解决方案。

　　一般地，在.NET中，多个控件之间重叠时是不会实现透明效果的。如下图所示：

　　下面开始介绍这几种解决方案：

　　第一种方案：记录不透明图片的路径，再设置透明效果。参考代码如下：

   /// <summary>
   /// PictureBox透明示例
    /// Date:2012-3-4 07:25:56
    /// </summary>
    public partial class Form1 : Form
    {
        [DllImport(“user32.dll“)]
        public static extern int ReleaseCapture();

[DllImport(“user32.dll“)]
public static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

        public const int WM_SYSCOMMAND = 0x0112;
        public const int SC_MOVE = 0xF010;
        public const int HTCAPTION = 0x0002;

        public Form1()
        {
            InitializeComponent();
            //this.picModelImage.Controls.Add(this.picHair);
        }

        private void picHair_MouseDown(object sender, MouseEventArgs e)
        {
            SetPictureBoxTransparent(picHair, picHair.Image);
            //SetPictureBoxTransparent(picModelImage, picModelImage.Image);
            ReleaseCapture();
            SendMessage(this.picHair.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
        }

        // 使用不安全的指针
        // 返回不透明的图片路径
        private unsafe GraphicsPath NoteGraphicsPath(Image image)
        {
            if (image == null)
                return null;

            // 声明GraphicsPath类以便计算位图路径
            GraphicsPath graphicsPath = new GraphicsPath(FillMode.Alternate);
            Bitmap bitmap = new Bitmap(image);

int picWidth = bitmap.Width;
int picHeight = bitmap.Height;

BitmapData bitmapdata = bitmap.LockBits(new Rectangle(0, 0, picWidth, picHeight), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

            byte* point = (byte*)bitmapdata.Scan0;
            int offset = bitmapdata.Stride – picWidth * 3;
            int p0, p1, p2;
            p0 = point[0];
            p1 = point[1];
            p2 = point[2];
            int start = –1;

            for (int h = 0; h < picHeight; h++)
            {
                for (int x = 0; x < picWidth; x++)
                {
                    // 如果之前的点没有不透明且不透明
                    if (start == –1 && (point[0] != p0 || point[1] != p1 || point[2] != p2))
                    {
                        start = x;
                    }
                    else if (start > –1 && (point[0] == p0 && point[1] == p1 && point[2] == p2))
                    {
                        // 如果之前的点是不透明
                        graphicsPath.AddRectangle(new Rectangle(start, h, x – start – 1, 1));
                        start = –1;
                    }

                    // 如果之前的点是不透明且是最后一个点
                    if (x == picWidth – 1 && start > –1)
                    {
                        graphicsPath.AddRectangle(new Rectangle(start, h, x – start + 1, 1));
                        start = –1;
                    }

point += 3;
}

point += offset;
}

bitmap.UnlockBits(bitmapdata);
bitmap.Dispose();

return graphicsPath;
}

        /// <summary>
        /// 需要设置透明效果的控件调用该方法
        /// </summary>
        /// <param name=”control”>要设置透明效果的控件</param>
        /// <param name=”image”>控件的图片</param>
        public void SetPictureBoxTransparent(Control control, Image image)
        {
            GraphicsPath graphic = null;
            graphic = NoteGraphicsPath(image);

if (graphic == null)
return;

control.Region = new Region(graphic);
}

}

　　需要添加2个命名空间：

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;

　　运行后效果如下所示：

　　注意：由于本示例有不安全的代码[关键字unsafe]，需要在项目属性中设置”允许不安全代码”，如下图：

　　第二种方案：使用GDI +中绘制图像与透明

　　这种方案是需要我使用GDI+绘制图像，具体步骤如下所示：

　　1. 需要添加两个组件类：

　　PictureBoxModel.cs 和 PanelExtend.cs

　　PanelExtend.cs 中代码：

using System;

using System.Drawing;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

/// <summary>
/// Panel扩展类
/// </summary>
public abstract class PanelExtend : Panel
{
protected Graphics graphics;

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x00000020; // 实现透明样式

            return cp;
        }
    }

    public PanelExtend()
    {
    }

    protected override void OnPaintBackground(PaintEventArgs pevent)
    {

    }

    protected override void OnPaint(PaintEventArgs e)
    {
        this.graphics = e.Graphics;

        this.graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
        this.graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
        this.graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
        this.graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

OnDraw();
}

protected abstract void OnDraw();

}

　　PictureBoxModel.cs 代码：

using System;

using System.Collections.Generic;
using System.Text;
using System.Drawing;

/// <summary>
/// 实现绘制图像
/// </summary>
public class PictureBoxModel : PanelExtend
{
    public PictureBoxModel()
    {
        //this.SetStyle(System.Windows.Forms.ControlStyles.SupportsTransparentBackColor, true);
    }

    protected override void OnDraw()
    {
        // 获取图像
        Image imageModel = global::MyPictureBoxDemo.Properties.Resources.model;
        Image imageHair = global::MyPictureBoxDemo.Properties.Resources.hair;

        //int width = imageModel.Size.Width;
        //int height = imageModel.Size.Height;

        int width = this.Width;
        int height = this.Height;
        Rectangle recModel = new Rectangle(0, 0, width, height);
        Rectangle recHair = new Rectangle(0, 0, imageHair.Width, imageHair.Height);

        this.graphics.DrawImage(imageModel, recModel);
        this.graphics.DrawImage(imageHair, recHair);
    }