图像变量为byte []数组

Question

I'm faced in a problem which i think is simple to solve, just i did something wrong, so: I have an Android tablet, where the user can draw signature, i get the image (.JPEG) by adb.

    ProcessStartInfo adb_copy = new ProcessStartInfo("C:/SCR/adb/adb.exe");
    adb_copy.Arguments = "pull \"mnt/sdcard/sign.jpg\" \"C:\\SCR\\temp\\sign.jpg\"";
    adb_copy.WindowStyle = ProcessWindowStyle.Hidden;
    Process.Start(adb_copy);

I have two Image variables:

Image WORKER_sign;
Image EMPLOYER_sign;

I load the image in these, and in a picturebox too:

    using (FileStream stream = new FileStream("C:/SCR/temp/sign.jpg", FileMode.Open, FileAccess.Read))
    {
        WORKER_sign = Image.FromStream(stream);
        stream.Close();
    }
    pictureBox3.Image = WORKER_sign;
    pictureBox3.SizeMode = PictureBoxSizeMode.Zoom;

The picturebox shows the images perfectly, however i can't write in a byte array. I tried the following code:

public static byte[] ImageToByte(Image img)
{
    if (img == null) return null;
    byte[] result;
    using (MemoryStream stream = new MemoryStream())
    {
        img.Save(stream, img.RawFormat);
        result = stream.GetBuffer();
    }
    return result;
}
byte[] temparray = ImageToByte(WORKER_SIGN);

But the last line throws me a Generic GDI+ exception, and before this the IntelliTrace shows some System.ObjectDisposedException ("Closed file") too.

What's wrong with my code? Thank you for all the help! :)

OFF: Sorry for my bad ENG...

EDIT: The errors:

Exception:Thrown: "Cannot access a closed Stream." (System.ObjectDisposedException) A System.ObjectDisposedException was thrown: "Cannot access a closed Stream." Time: 2014.08.11. 14:37:49 Thread:Main Thread[7276]

Exception:Thrown: "Generic error in: GDI+." (System.Runtime.InteropServices.ExternalException) A System.Runtime.InteropServices.ExternalException was thrown: "Generic error in: GDI+." Time: 2014.08.11. 14:37:49 Thread:Main Thread[7276]

Answer 1

Change your code to:

public static byte[] ImageToByte(Image img)
{
    if (img == null) return null;
    byte[] result;
    using (MemoryStream stream = new MemoryStream())
    {
        img.Save(stream, img.RawFormat);
        result = stream.ToArray();
    }
    return result;
}

Answer 2

Thanks for everbody who helped me, I'm figured out the things by this code:

    EMPLOYER_SIGN = new Bitmap(426, 155);
    using (Graphics gr = Graphics.FromImage(EMPLOYER_SIGN))
    {
        gr.SmoothingMode = SmoothingMode.HighQuality;
        gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
        gr.PixelOffsetMode = PixelOffsetMode.HighQuality;
        gr.DrawImage(Image.FromFile("C:/SCR/temp/sign.jpg"), new Rectangle(0, 0, 426, 155));
    }
    MemoryStream ms = new MemoryStream();
    EMPLOYER_SIGN.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    BARRAY_EMPSIGN = ms.ToArray();
    ms.Dispose();
    pictureBox3.Image = EMPLOYER_SIGN;