public void TestCreateCompatibleDc()
{
using (var desktopDcHandle = SafeWindowDcHandle.FromDesktop())
{
Assert.False(desktopDcHandle.IsInvalid);
// create a device context we can copy to
using (var safeCompatibleDcHandle = Gdi32Api.CreateCompatibleDC(desktopDcHandle))
{
Assert.False(safeCompatibleDcHandle.IsInvalid);
}
}
}
/// <summary>
/// This method will use User32 code to capture the specified captureBounds from the screen
/// </summary>
/// <param name="captureBounds">NativeRect with the bounds to capture</param>
/// <returns>Bitmap which is captured from the screen at the location specified by the captureBounds</returns>
public static Bitmap CaptureRectangle(NativeRect captureBounds)
{
Bitmap returnBitmap = null;
if (captureBounds.Height <= 0 || captureBounds.Width <= 0)
{
Log.Warn().WriteLine("Nothing to capture, ignoring!");
return(null);
}
Log.Debug().WriteLine("CaptureRectangle Called!");
// .NET GDI+ Solution, according to some post this has a GDI+ leak...
// See http://connect.microsoft.com/VisualStudio/feedback/details/344752/gdi-object-leak-when-calling-graphics-copyfromscreen
// Bitmap capturedBitmap = new Bitmap(captureBounds.Width, captureBounds.Height);
// using (Graphics graphics = Graphics.FromImage(capturedBitmap)) {
// graphics.CopyFromScreen(captureBounds.Location, NativePoint.Empty, captureBounds.Size, CopyPixelOperation.CaptureBlt);
// }
// capture.Image = capturedBitmap;
// capture.Location = captureBounds.Location;
using (var desktopDcHandle = SafeWindowDcHandle.FromDesktop())
{
if (desktopDcHandle.IsInvalid)
{
// Get Exception before the error is lost
var exceptionToThrow = CreateCaptureException("desktopDCHandle", captureBounds);
// throw exception
throw exceptionToThrow;
}
// create a device context we can copy to
using (var safeCompatibleDcHandle = Gdi32Api.CreateCompatibleDC(desktopDcHandle))
{
// Check if the device context is there, if not throw an error with as much info as possible!
if (safeCompatibleDcHandle.IsInvalid)
{
// Get Exception before the error is lost
var exceptionToThrow = CreateCaptureException("CreateCompatibleDC", captureBounds);
// throw exception
throw exceptionToThrow;
}
// Create BITMAPINFOHEADER for CreateDIBSection
var bmi = BitmapInfoHeader.Create(captureBounds.Width, captureBounds.Height, 24);
// TODO: Enable when the function is available again
// Make sure the last error is set to 0
Win32.SetLastError(0);
// create a bitmap we can copy it to, using GetDeviceCaps to get the width/height
IntPtr bits0; // not used for our purposes. It returns a pointer to the raw bits that make up the bitmap.
// TODO: Change the usage to an enum?
using (var safeDibSectionHandle = Gdi32Api.CreateDIBSection(desktopDcHandle, ref bmi, 0, out bits0, IntPtr.Zero, 0))
{
if (safeDibSectionHandle.IsInvalid)
{
// Get Exception before the error is lost
var exceptionToThrow = CreateCaptureException("CreateDIBSection", captureBounds);
exceptionToThrow.Data.Add("hdcDest", safeCompatibleDcHandle.DangerousGetHandle().ToInt32());
exceptionToThrow.Data.Add("hdcSrc", desktopDcHandle.DangerousGetHandle().ToInt32());
// Throw so people can report the problem
throw exceptionToThrow;
}
// select the bitmap object and store the old handle
using (safeCompatibleDcHandle.SelectObject(safeDibSectionHandle))
{
// bitblt over (make copy)
// ReSharper disable once BitwiseOperatorOnEnumWithoutFlags
Gdi32Api.BitBlt(safeCompatibleDcHandle, 0, 0, captureBounds.Width, captureBounds.Height, desktopDcHandle, captureBounds.X, captureBounds.Y,
RasterOperations.SourceCopy | RasterOperations.CaptureBlt);
}
// get a .NET image object for it
// A suggestion for the "A generic error occurred in GDI+." E_FAIL/0×80004005 error is to re-try...
var success = false;
ExternalException exception = null;
for (var i = 0; i < 3; i++)
{
try
{
// Collect all screens inside this capture
var screensInsideCapture = new List <Screen>();
foreach (var screen in Screen.AllScreens)
{
if (screen.Bounds.IntersectsWith(captureBounds))
{
screensInsideCapture.Add(screen);
}
}
// Check all all screens are of an equal size
bool offscreenContent;
using (var captureRegion = new Region(captureBounds))
{
// Exclude every visible part
foreach (var screen in screensInsideCapture)
{
captureRegion.Exclude(screen.Bounds);
}
// If the region is not empty, we have "offscreenContent"
using (var screenGraphics = Graphics.FromHwnd(User32Api.GetDesktopWindow()))
{
offscreenContent = !captureRegion.IsEmpty(screenGraphics);
}
}
// Check if we need to have a transparent background, needed for offscreen content
if (offscreenContent)
{
using (var tmpBitmap = Image.FromHbitmap(safeDibSectionHandle.DangerousGetHandle()))
{
// Create a new bitmap which has a transparent background
returnBitmap = BitmapFactory.CreateEmpty(tmpBitmap.Width, tmpBitmap.Height, PixelFormat.Format32bppArgb, Color.Transparent, tmpBitmap.HorizontalResolution,
tmpBitmap.VerticalResolution);
// Content will be copied here
using (var graphics = Graphics.FromImage(returnBitmap))
{
// For all screens copy the content to the new bitmap
foreach (var screen in Screen.AllScreens)
{
// Make sure the bounds are offsetted to the capture bounds
var screenBounds = screen.Bounds;
screenBounds.Offset(-captureBounds.X, -captureBounds.Y);
graphics.DrawImage(tmpBitmap, screenBounds, screenBounds.X, screenBounds.Y, screenBounds.Width, screenBounds.Height, GraphicsUnit.Pixel);
}
}
}
}
else
{
// All screens, which are inside the capture, are of equal size
// assign image to Capture, the image will be disposed there..
returnBitmap = Image.FromHbitmap(safeDibSectionHandle.DangerousGetHandle());
}
// We got through the capture without exception
success = true;
break;
}
catch (ExternalException ee)
{
Log.Warn().WriteLine(ee, "Problem getting bitmap at try " + i + " : ");
exception = ee;
}
}
if (!success)
{
Log.Error().WriteLine(null, "Still couldn't create Bitmap!");
if (exception != null)
{
throw exception;
}
}
}
}
}
return(returnBitmap);
}