Added option to include layered windows in ImageGrab.grab on Windows

Tests/test_imagegrab.py

@@ -9,8 +9,11 @@
     class TestImageGrab(PillowTestCase):
 
         def test_grab(self):
-            im = ImageGrab.grab()
-            self.assert_image(im, im.mode, im.size)
+            for im in [
+                ImageGrab.grab(),
+                ImageGrab.grab(include_layered_windows=True)
+            ]:
+                self.assert_image(im, im.mode, im.size)
 
         def test_grabclipboard(self):
             if sys.platform == "darwin":

docs/reference/ImageGrab.rst

@@ -11,7 +11,7 @@ or the clipboard to a PIL image memory.
 
 .. versionadded:: 1.1.3
 
-.. py:function:: PIL.ImageGrab.grab(bbox=None)
+.. py:function:: PIL.ImageGrab.grab(bbox=None, include_layered_windows=False)
 
     Take a snapshot of the screen. The pixels inside the bounding box are
     returned as an "RGB" image on Windows or "RGBA" on macOS.
@@ -20,6 +20,7 @@ or the clipboard to a PIL image memory.
     .. versionadded:: 1.1.3 (Windows), 3.0.0 (macOS)
 
     :param bbox: What region to copy. Default is the entire screen.
+    :param include_layered_windows: Includes layered windows. Windows OS only.
     :return: An image
 
 .. py:function:: PIL.ImageGrab.grabclipboard()

src/PIL/ImageGrab.py

@@ -29,7 +29,7 @@
     import subprocess
 
 
-def grab(bbox=None):
+def grab(bbox=None, include_layered_windows=False):
     if sys.platform == "darwin":
         fh, filepath = tempfile.mkstemp('.png')
         os.close(fh)
@@ -38,7 +38,7 @@ def grab(bbox=None):
         im.load()
         os.unlink(filepath)
     else:
-        size, data = grabber()
+        size, data = grabber(include_layered_windows)
         im = Image.frombytes(
             "RGB", size, data,
             # RGB, 32-bit line padding, origin lower left corner

src/display.c

@@ -323,11 +323,16 @@ PyObject*
 PyImaging_GrabScreenWin32(PyObject* self, PyObject* args)
 {
     int width, height;
+    int includeLayeredWindows = 0;
     HBITMAP bitmap;
     BITMAPCOREHEADER core;
     HDC screen, screen_copy;
+    DWORD rop;
     PyObject* buffer;
 
+    if (!PyArg_ParseTuple(args, "|i", &includeLayeredWindows))
+        return NULL;
+
     /* step 1: create a memory DC large enough to hold the
        entire screen */
 
@@ -346,7 +351,10 @@ PyImaging_GrabScreenWin32(PyObject* self, PyObject* args)
 
     /* step 2: copy bits into memory DC bitmap */
 
-    if (!BitBlt(screen_copy, 0, 0, width, height, screen, 0, 0, SRCCOPY))
+    rop = SRCCOPY;
+    if (includeLayeredWindows)
+        rop |= CAPTUREBLT;
+    if (!BitBlt(screen_copy, 0, 0, width, height, screen, 0, 0, rop))
         goto error;
 
     /* step 3: extract bits from bitmap */