教你实现Winform窗体的四边阴影效果

小咪咪 2022-08-13 14:43 386阅读 0赞

本文转载于CSKIN论坛，地址：[http://bbs.cskin.net/thread-61-1-1.html][http_bbs.cskin.net_thread-61-1-1.html]

1.首先我们得有这样一张阴影图片。

![112732ra5l9ztf5lf7ll84.png][]

2.然后分别有两个窗体去实现这个阴影效果。

*  SkinForm \- 用于实现阴影的绘制，特性：鼠标可穿透，无法点击，跟随窗体。
 *  SkinMain \- 主窗体，也是承载控件的容器窗体， 特性：与普通窗体无一区别，移动和拉伸，阴影窗体都会跟随。

3.在 SkinMain主窗体的 OnVisibleChanged事件中new出阴影窗体

*  //绘制层
 *  private SkinForm skin;
 *  skin = new SkinForm(this);
 *  skin.Show(this);

4.阴影窗体中绘制不规则透明图片的代码：

public void SetBits() {
        //绘制绘图层背景
        Bitmap bitmap = new Bitmap(Main.Width + 10, Main.Height + 10);
        Rectangle _BacklightLTRB = new Rectangle(20, 20, 20, 20);//窗体光泽重绘边界
        Graphics g = Graphics.FromImage(bitmap);
        g.SmoothingMode = SmoothingMode.HighQuality; //高质量
        g.PixelOffsetMode = PixelOffsetMode.HighQuality; //高像素偏移质量
        ImageDrawRect.DrawRect(g, Properties.Resources.main_light_bkg_top123, ClientRectangle, Rectangle.FromLTRB(_BacklightLTRB.X, _BacklightLTRB.Y, _BacklightLTRB.Width, _BacklightLTRB.Height), 1, 1);
     
        if (!Bitmap.IsCanonicalPixelFormat(bitmap.PixelFormat) || !Bitmap.IsAlphaPixelFormat(bitmap.PixelFormat))
            throw new ApplicationException("图片必须是32位带Alhpa通道的图片。");
        IntPtr oldBits = IntPtr.Zero;
        IntPtr screenDC = Win32.GetDC(IntPtr.Zero);
        IntPtr hBitmap = IntPtr.Zero;
        IntPtr memDc = Win32.CreateCompatibleDC(screenDC);
     
        try {
            Win32.Point topLoc = new Win32.Point(Left, Top);
            Win32.Size bitMapSize = new Win32.Size(Width, Height);
            Win32.BLENDFUNCTION blendFunc = new Win32.BLENDFUNCTION();
            Win32.Point srcLoc = new Win32.Point(0, 0);
     
            hBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
            oldBits = Win32.SelectObject(memDc, hBitmap);
     
            blendFunc.BlendOp = Win32.AC_SRC_OVER;
            blendFunc.SourceConstantAlpha = Byte.Parse("255");
            blendFunc.AlphaFormat = Win32.AC_SRC_ALPHA;
            blendFunc.BlendFlags = 0;
     
            Win32.UpdateLayeredWindow(Handle, screenDC, ref topLoc, ref bitMapSize, memDc, ref srcLoc, 0, ref blendFunc, Win32.ULW_ALPHA);
        } finally {
            if (hBitmap != IntPtr.Zero) {
                Win32.SelectObject(memDc, oldBits);
                Win32.DeleteObject(hBitmap);
            }
            Win32.ReleaseDC(IntPtr.Zero, screenDC);
            Win32.DeleteDC(memDc);
        }
    }

效果图：  
![113417b26a5fj4ptct2czj.png][]

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[112732ra5l9ztf5lf7ll84.png]: /images/20220810/9022e76b4d194df7a6b2715992681ea8.png
[113417b26a5fj4ptct2czj.png]: /images/20220810/41e8e004f386498883ec58f02825a9ec.png