using System.Drawing;
using System.Drawing.Imaging;
<summary>
</summary>
<param name="sourceImage"></param>
<returns></returns>
public static Image CreateAlphaImage(Image sourceImage)
{
int imageWidth = sourceImage.Width;
int imageHeight = sourceImage.Height;
Bitmap alphaImage = new Bitmap(imageWidth, imageHeight);
using (Graphics g = Graphics.FromImage(alphaImage))
{
ColorMatrix cm = new ColorMatrix();
cm.Matrix00 = 1;
cm.Matrix11 = 1;
cm.Matrix22 = 1;
cm.Matrix33 = 0.5F;
cm.Matrix44 = 1;
ImageAttributes ia = new ImageAttributes();
ia.SetColorMatrix(cm);
g.DrawImage(sourceImage,
new Rectangle(0, 0, imageWidth, imageHeight),
0,
0,
imageWidth,
imageHeight,
GraphicsUnit.Pixel,
ia);
}
return alphaImage;
}