Bitmap.MakeTransparent Method ()


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Makes the default transparent color transparent for this Bitmap.

Namespace:   System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

public void MakeTransparent()

Exception Condition

The image format of the Bitmap is an icon format.


The operation failed.

The system palette defines one color as the default transparent, or alpha, color. This method makes the default transparent color transparent for this Bitmap. If no transparent color is specified by the system, LightGray is the transparent color.

When you call MakeTransparent, the bitmap will be converted to the Format32bppArgb format, as this format supports an alpha channel.

The following code example is designed for use with Windows Forms, and it requires PaintEventArgse, which is a parameter of the Paint event handler. The code makes the system default transparent color transparent for myBitmap, and then draws the Bitmap to the screen.

private void MakeTransparent_Example1(PaintEventArgs e)

    // Create a Bitmap object from an image file.
    Bitmap myBitmap = new Bitmap("Grapes.gif");

    // Draw myBitmap to the screen.
    e.Graphics.DrawImage(myBitmap, 0, 0, myBitmap.Width,

    // Make the default transparent color transparent for myBitmap.

    // Draw the transparent bitmap to the screen.
    e.Graphics.DrawImage(myBitmap, myBitmap.Width, 0,
        myBitmap.Width, myBitmap.Height);

.NET Framework
Available since 1.1
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