问如何在C#中从Graphics对象中获取位图/图像？

EN

// Create a new bitmap object
using (Bitmap bmp = new Bitmap(200, 300))
{
    // Obtain a Graphics object from that bitmap
    using (Graphics g = Graphics.FromImage(bmp))
    {
        // Draw onto the bitmap here
        // ....
        g.DrawRectangle(Pens.Red, 10, 10, 50, 50);
    }

    // Save the bitmap to a file on disk, or do whatever else with it
    // ...
    bmp.Save("C:\\MyImage.bmp");
}

System.Drawing.Image originalImage = //your image

//Create empty bitmap image of original size

Bitmap tempBmp = new Bitmap(originalImage.Width, originalImage.Height);

Graphics g = Graphics.FromImage(tempBmp);

//draw the original image on tempBmp

g.DrawImage(originalImage, 0, 0, originalImage.Width, originalImage.Height);

//dispose originalImage and Graphics so the file is now free

g.Dispose();

originalImage.Dispose();

using (MemoryStream ms = new MemoryStream())
{
    // Convert Image to byte[]
    tempBmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    //dpgraphic.image.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
    byte[] imageBytes = ms.ToArray();

    // Convert byte[] to Base64 String
    string strImage = Convert.ToBase64String(imageBytes);
    sb.AppendFormat(strImage);
}

// System.Windows.Forms.Internal.IntUnsafeNativeMethods
[DllImport("gdi32.dll", CharSet = CharSet.Auto, EntryPoint = "GetCurrentObject", ExactSpelling = true, SetLastError = true)]
public static extern IntPtr IntGetCurrentObject(HandleRef hDC, int uObjectType);


IntPtr hdc = graphics.GetHdc();
// This is a HBITMAP, which is the actual buffer that is being drawn to by hdc.
IntPtr hbitmap = IntGetCurrentObject(new HandleRef(null, hdc), 7 /*OBJ_BITMAP*/);
// You can create a Gdiplus::Bitmap object from this, but it will copy all image data.
//Bitmap bitmap = Image.FromHbitmap(hbitmap);
// To manipulate the actual bitmap pixel data directly, see below.

// Put these in finally:
//bitmap.Dispose();
// NOTE: You cannot use the graphics object before ReleaseHdc is called.
graphics.ReleaseHdc(hdc);

[DllImport("gdi32.dll")]
static extern unsafe int GetObject(IntPtr hobj, int cb, void* data);

[StructLayout(LayoutKind.Sequential)]
unsafe struct BITMAP
{
    int        bmType;
    int        bmWidth;
    int        bmHeight;
    int        bmWidthBytes;
    ushort     bmPlanes;
    ushort     bmBitsPixel;
    void*      bmBits;
}

BITMAP BitmapDesc = new BITMAP();
GetObject(hbitmap, sizeof(BITMAP), &BitmapDesc);