public System.Drawing.Bitmap KnockOutGzf(String path)
{
System.Drawing.Image image = System.Drawing.Image.FromFile(path);
System.Drawing.Bitmap bitmapProxy = new System.Drawing.Bitmap(image);
image.Dispose();
for (int i = 0; i < bitmapProxy.Width; i++)
{
for (int j = 0; j < bitmapProxy.Height; j++)
{
System.Drawing.Color c = bitmapProxy.GetPixel(i, j);
if (!(c.R < 240 || c.G < 240 || c.B < 240))
{
bitmapProxy.SetPixel(i, j, System.Drawing.Color.Transparent);
}
}
}
return bitmapProxy;
}
引用：https://www.cnblogs.com/guozefeng/p/4178291.html