Bitmap.MakeTransparent Method

Definition

Namespace:

System.Drawing

Assembly:

System.Drawing.Common.dll

Makes the default transparent color transparent for this Bitmap.

Overloads

MakeTransparent()	Makes the default transparent color transparent for this Bitmap.
MakeTransparent(Color)	Makes the specified color transparent for this Bitmap.

MakeTransparent()

Source:

Bitmap.cs

Makes the default transparent color transparent for this Bitmap.

C#

public void MakeTransparent();

Exceptions

InvalidOperationException

The image format of the Bitmap is an icon format.

Exception

The operation failed.

Examples

The following code example is designed for use with Windows Forms, and it requires PaintEventArgs e, 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.

C#

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,
        myBitmap.Height);

    // Make the default transparent color transparent for myBitmap.
    myBitmap.MakeTransparent();

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

Remarks

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.

MakeTransparent(Color)

Source:

Bitmap.cs

Makes the specified color transparent for this Bitmap.

C#

public void MakeTransparent(System.Drawing.Color transparentColor);

Parameters

transparentColor

Color

The Color structure that represents the color to make transparent.

Exceptions

InvalidOperationException

The image format of the Bitmap is an icon format.

Exception

The operation failed.

Examples

The following code example is designed for use with Windows Forms, and it requires PaintEventArgs e, which is a parameter of the Paint event handler. The code performs the following actions:

• Gets the color of a pixel in a Bitmap.

• Makes that color transparent for the bitmap.

• Draws the Bitmap to the screen.

C#

private void MakeTransparent_Example2(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, myBitmap.Height);

    // Get the color of a background pixel.
    Color backColor = myBitmap.GetPixel(1, 1);

    // Make backColor transparent for myBitmap.
    myBitmap.MakeTransparent(backColor);

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

Remarks

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