[Mono-list] screen capturing in mono
Scott Willeke
scott at willeke.com
Wed Feb 28 16:39:02 EST 2007
In theory you could use reflection to call the protected Control.OnPaint
method to trick it into painting on your bitmap's graphics, but it is
obviously a hack, and may have security implications (will almost
certainly require full trust, especially on MS.NET).
Sebastien Pouliot wrote:
> On Wed, 2007-02-28 at 15:34 -0500, Abe Gillespie wrote:
>
>> Have you tried the DrawToBitmap method?
>>
>
> Nice one, but 2.0 and not yet implemented in Mono.
>
>
>> -Abe
>>
>> On 2/28/07, Eric Morgan <eric at rengeo.com> wrote:
>>
>>> 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
>>>>>
>>>>>
>>>>>
>>>>
>>> _______________________________________________
>>> 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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> http://lists.ximian.com/mailman/listinfo/mono-list
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