C#图片格式转换

using (Bitmap bmp = new Bitmap(@"E:\test.jpg"))
{
    bmp.Save(@"E:\test.bmp", ImageFormat.Bmp);
}

using (Bitmap bmp = new Bitmap(@"E:\test.jpg"))
{
    using (Bitmap bmp2 = new Bitmap(bmp, 100, 100))
    {
        bmp2.Save(@"E:\test.png", ImageFormat.Png);
    }
}