[Mono-list] screen capturing in mono

[Eric Morgan]

I'm not too sure how to get a Bitmap object from a graphics object.  From
all I've read, I just hear that you have to deal with device contexts.  I'm
not too familiar with it, but BitBlt seems to be the way to do that.  What
would I need to do to get that bitmap created with what appears in the
control using 100% .NET so it can run in mono?  Here's a snippet of code.

        [System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]
        private static extern bool BitBlt(
            IntPtr hdcDest, // handle to destination DC
            int nXDest,  // x-coord of destination upper-left corner
            int nYDest,  // y-coord of destination upper-left corner
            int nWidth,  // width of destination rectangle
            int nHeight, // height of destination rectangle
            IntPtr hdcSrc,  // handle to source DC
            int nXSrc,   // x-coordinate of source upper-left corner
            int nYSrc,   // y-coordinate of source upper-left corner
            System.Int32 dwRop  // raster operation code
            );


        public static Bitmap PerformCapture(Control c, int maxWidth, int
maxHeight)
        {
            try
            {
                int w = c.ClientRectangle.Width;
                int h = c.ClientRectangle.Height;

                w = System.Math.Min(w, maxWidth);
                h = System.Math.Min(w, maxHeight);

                System.Drawing.Graphics g1 = c.CreateGraphics
();//this.CreateGraphics();
                Bitmap MyImage = new Bitmap(w, h, g1);
                System.Drawing.Graphics g2 =
System.Drawing.Graphics.FromImage(MyImage);
                IntPtr dc1 = g1.GetHdc();
                IntPtr dc2 = g2.GetHdc();
                BitBlt(dc2, 0, 0, w, h, dc1, 0, 0, 13369376);
                g1.ReleaseHdc(dc1);
                g2.ReleaseHdc(dc2);

//Separate dialog to display the image.  If I comment out the BitBlt code,
it just appears blank.
                Library.Windows.Dialogs.ScreenCaptureDlg dlg = new
Library.Windows.Dialogs.ScreenCaptureDlg(MyImage);
                dlg.ShowDialog();

                return MyImage;
            }
            catch(Exception error)
            {
//our exception handling library.
                Library.Common.ErrMsg.Err( error );
                throw error;
            }
        }



On 2/28/07, Abe Gillespie <abe.gillespie at gmail.com> wrote:
>
> Are you P/Invoking for performance?  Why not just use the GDI .Net API?
>
> -Abe
>
> On 2/28/07, Eric Morgan <eric at rengeo.com> wrote:
> > Hi all,
> >
> > Is there a good way to capture screens or something similar in mono?  In
> our
> > .NET application, we have custom controls, and we basically create a
> > graphics object from it, make a new bitmap, then do a bitblt to get it
> into
> > the bitmap.  This requires a P/Invoke into gdi32.dll, which obviously
> blows
> > up in mono.  Is there a good way to do this using mono?  Some other
> library
> > maybe?
> >
> > I've tried installing wine and using the gdi32.dll.so that comes with
> it,
> > but I don't know if I'm using it correctly or not.  It can find the
> library,
> > but it gives a SIGSEGV while trying to execute the bitblt
> operation.  Seemed
> > like kind of a hack, and I didn't really expect it to work...  Do I need
> > other libraries along with the gdi32.dll.so ?
> >
> > Any advice is appreciated.  Thanks.
> >
> > Eric Morgan
> > Renegade Geophysics
> > 303-661-0400, x2
> >
> > _______________________________________________
> > Mono-list maillist  -  Mono-list at lists.ximian.com
> > http://lists.ximian.com/mailman/listinfo/mono-list
> >
> >
>
>
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