Transparent control over PictureBox

问题:

In my C# Form I have a Label that displays a download percentage in the download event:

  this.lblprg.Text = overallpercent.ToString(\"#0\") + \"%\";

The Label control\'s BackColor property is set to be transparent and I want it to be displayed over a PictureBox. But that doesn\'t appear to work correctly, I see a gray background, it doesn\'t look transparent on top of the picture box. How can I fix this?

回答1:

The Label control supports transparency well. It is just that the designer won\'t let you place the label correctly. The PictureBox control is not a container control so the Form becomes the parent of the label. So you see the form\'s background.

It is easy to fix by adding a bit of code to the form constructor. You\'ll need to change the label\'s Parent property and recalculate it\'s Location since it is now relative to the picture box instead of the form. Like this:

    public Form1() {
        InitializeComponent();
        var pos = this.PointToScreen(label1.Location);
        pos = pictureBox1.PointToClient(pos);
        label1.Parent = pictureBox1;
        label1.Location = pos;
        label1.BackColor = Color.Transparent;
    }

Looks like this at runtime:

---

Another approach is to solve the design-time problem. That just takes an attribute. Add a reference to System.Design and add a class to your project, paste this code:

using System.ComponentModel;
using System.Windows.Forms;
using System.Windows.Forms.Design;    // Add reference to System.Design

[Designer(typeof(ParentControlDesigner))]
class PictureContainer : PictureBox {}

回答2:

You can just use

label1.Parent = pictureBox1;
label1.BackColor = Color.Transparent; // You can also set this in the designer, as stated by ElDoRado1239

回答3:

You can draw text using TextRenderer which will draw it without background:

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    TextRenderer.DrawText(e.Graphics, 
                          overallpercent.ToString(\"#0\") + \"%\", 
                          this.Font, 
                          new Point(10, 10), 
                          Color.Red);
}

When overallpercent value changes, refresh pictureBox:

pictureBox1.Refresh();

You can also use Graphics.DrawString but TextRenderer.DrawText (using GDI) is faster than DrawString (GDI+)

Also look at another answer here and DrawText reference here

回答4:

For easy for your design. You can place your label inside a panel. and set background image of panel is what every image you want. set label background is transparent

回答5:

Using Visual Studio with Windows Form you may apply transparency to labels or other elements by adding using System.Drawing; into Form1.Designer.cs This way you will have Transparency available from the Properties panel ( in Appearance at BackColor ). Or just edit code in Designer.cs this.label1.BackColor = System.Drawing.Color.Transparent;