要制作透明层，您应该覆盖控件的绘制并按此顺序绘制控件，首先在同一容器中绘制您控制下的所有控件（基于 z-index ) 在位图上。
然后在控件的图形上绘制该位图。
最后绘制控件的内容。
另外你的控件的BackColor应该是Color.Transparent。
作为制作透明层的另一个选项，您可以在绘制时从您的控件中排除某些区域。
在以下示例中，我使用了第一种技术并创建了 2 个控件。一个spinning circles 透明控件。和一个transparent picturebox 控件。
在这两个示例中，我使用了加载行之间的延迟来显示微调器。
示例 1 - 使用 SpinningCircles 控件
SpinningCircles 控件绘制圆圈并支持透明度。控件在设计时不动画，但在运行时动画。不可见时也不会消耗资源。
示例 2 - 使用透明图片框控件和透明动画 gif
TransparentPictureBox 控件支持透明度，因此我使用了动画 gif 作为其图像，如您所见，gif 显示正确。
示例 1 代码 - SpinningCircles
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Windows.Forms;
public class SpinningCircles : Control
{
int increment = 1;
int radius = 4;
int n = 8;
int next = 0;
Timer timer;
public SpinningCircles()
{
timer = new Timer();
this.Size = new Size(100, 100);
timer.Tick += (s, e) => this.Invalidate();
if (!DesignMode)
timer.Enabled = true;
SetStyle(ControlStyles.AllPaintingInWmPaint |
ControlStyles.OptimizedDoubleBuffer |
ControlStyles.ResizeRedraw | ControlStyles.UserPaint |
ControlStyles.SupportsTransparentBackColor, true);
BackColor = Color.Transparent;
}
protected override void OnPaint(PaintEventArgs e)
{
if (Parent != null && this.BackColor == Color.Transparent)
{
using (var bmp = new Bitmap(Parent.Width, Parent.Height))
{
Parent.Controls.Cast<Control>()
.Where(c => Parent.Controls.GetChildIndex(c) > Parent.Controls.GetChildIndex(this))
.Where(c => c.Bounds.IntersectsWith(this.Bounds))
.OrderByDescending(c => Parent.Controls.GetChildIndex(c))
.ToList()
.ForEach(c => c.DrawToBitmap(bmp, c.Bounds));
e.Graphics.DrawImage(bmp, -Left, -Top);
}
}
e.Graphics.SmoothingMode = SmoothingMode.HighQuality;
int length = Math.Min(Width, Height);
PointF center = new PointF(length / 2, length / 2);
int bigRadius = length / 2 - radius - (n - 1) * increment;
float unitAngle = 360 / n;
if (!DesignMode)
next++;
next = next >= n ? 0 : next;
int a = 0;
for (int i = next; i < next + n; i++)
{
int factor = i % n;
float c1X = center.X + (float)(bigRadius * Math.Cos(unitAngle * factor * Math.PI / 180));
float c1Y = center.Y + (float)(bigRadius * Math.Sin(unitAngle * factor * Math.PI / 180));
int currRad = radius + a * increment;
PointF c1 = new PointF(c1X - currRad, c1Y - currRad);
e.Graphics.FillEllipse(Brushes.Black, c1.X, c1.Y, 2 * currRad, 2 * currRad);
using (Pen pen = new Pen(Color.White, 2))
e.Graphics.DrawEllipse(pen, c1.X, c1.Y, 2 * currRad, 2 * currRad);
a++;
}
}
protected override void OnVisibleChanged(EventArgs e)
{
timer.Enabled = Visible;
base.OnVisibleChanged(e);
}
}
示例 2 代码 - 透明图片框代码
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Windows.Forms;
class TransparentPictureBox : PictureBox
{
public TransparentPictureBox()
{
this.BackColor = Color.Transparent;
}
protected override void OnPaint(PaintEventArgs e)
{
if (Parent != null && this.BackColor == Color.Transparent)
{
using (var bmp = new Bitmap(Parent.Width, Parent.Height))
{
Parent.Controls.Cast<Control>()
.Where(c => Parent.Controls.GetChildIndex(c) > Parent.Controls.GetChildIndex(this))
.Where(c => c.Bounds.IntersectsWith(this.Bounds))
.OrderByDescending(c => Parent.Controls.GetChildIndex(c))
.ToList()
.ForEach(c => c.DrawToBitmap(bmp, c.Bounds));
e.Graphics.DrawImage(bmp, -Left, -Top);
}
}
base.OnPaint(e);
}
}