[Mono-list] screen capturing in mono

[Eric Morgan]

The problem isn't resizing - I don't have an original bitmap to resize.  The
problem is that I have a control that I want a screenshot of.  So, I'm
trying to create a Bitmap from whatever is appearing in the control.

I pass the control in, then I call control.CreateGraphics();
System.Drawing.Graphics g1 = c.CreateGraphics();

Then, with the resulting graphics object, I try to create a new bitmap.
Bitmap MyImage = new Bitmap(w, h, g1);

The thing is, this bitmap is blank, unless I paste back in that BitBlt
code.  I can't figure out how to get a new bitmap from a graphics object,
without BitBlt().

Sebastien - Using 2.0 isn't an option, unfortunately.

Is there any alternative from P/Invoking in this case?

Thanks for all the help!

Eric

On 2/28/07, Abe Gillespie <abe.gillespie at gmail.com> wrote:
>
> It looks like you're just taking the image and resizing it to show in
> the dialog.  You really should not have to go into native OS libraries
> to do so.  Does this site help?
>
> http://www.peterprovost.org/archive/2003/05/29/516.aspx
>
> -Abe
>
> On 2/28/07, Eric Morgan <eric at rengeo.com> wrote:
> > 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
> > > >
> > > >
> > >
> > >
> >
> >
> > _______________________________________________
> > Mono-list maillist  -  Mono-list at lists.ximian.com
> > http://lists.ximian.com/mailman/listinfo/mono-list
> >
> >
>
>
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