Mac: Fix for the fix about 16 rounded width

Mickaël Schoentgen · Mickaël Schoentgen · commit 96b18f698d33 · 2017-08-31T08:50:49.000+02:00
Original patch by @DavideBecker and @redodo.
diff --git a/CHANGES.rst b/CHANGES.rst
@@ -8,6 +8,7 @@ base.py
 darwin.py
 ---------
 - Removed `get_infinity()` function
+- Removed `resize()` method. Use `_crop_width()` method instead.
 
 windows.py
 ----------
diff --git a/docs/source/examples.rst b/docs/source/examples.rst
@@ -5,17 +5,23 @@ Examples
 Basics
 ======
 
-One screenshot per monitor::
+One screenshot per monitor
+--------------------------
+::
 
     for filename in sct.save():
         print(filename)
 
-Screenshot of the monitor 1::
+Screenshot of the monitor 1
+---------------------------
+::
 
     filename = sct.shot()
     print(filename)
 
-A screenshot to grab them all::
+A screenshot to grab them all
+-----------------------------
+::
 
     filename = sct.shot(mon=-1, output='fullscreen.png')
     print(filename)
@@ -28,13 +34,6 @@ Screenshot of the monitor 1 with a callback:
 .. literalinclude:: examples/callback.py
     :lines: 9-
 
-GNU/Linux
----------
-
-On GNU/Linux, you can specify which display to use (useful for distant screenshots via SSH):
-
-.. literalinclude:: examples/linux_display_keyword.py
-    :lines: 9-
 
 Part of the screen
 ------------------
diff --git a/docs/source/usage.rst b/docs/source/usage.rst
@@ -33,3 +33,17 @@ So the module can be used as simply as::
 Or::
 
     sct = mss()
+
+
+GNU/Linux
+---------
+
+On GNU/Linux, you can specify which display to use (useful for distant screenshots via SSH)::
+
+    with mss(display=':0.0') as sct:
+        # ...
+
+A more specific example to only target GNU/Linux:
+
+.. literalinclude:: examples/linux_display_keyword.py
+    :lines: 9-
diff --git a/mss/darwin.py b/mss/darwin.py
@@ -93,6 +93,7 @@ def _set_argtypes(self):
             ctypes.c_uint32,
             ctypes.c_uint32,
             ctypes.c_uint32]
+        self.core.CGImageGetWidth.argtypes = [ctypes.c_void_p]
         self.core.CGImageGetDataProvider.argtypes = [ctypes.c_void_p]
         self.core.CGDataProviderCopyData.argtypes = [ctypes.c_void_p]
         self.core.CFDataGetBytePtr.argtypes = [ctypes.c_void_p]
@@ -110,6 +111,7 @@ def _set_restypes(self):
         self.core.CGRectUnion.restype = CGRect
         self.core.CGDisplayRotation.restype = ctypes.c_float
         self.core.CGWindowListCreateImage.restype = ctypes.c_void_p
+        self.core.CGImageGetWidth.restype = ctypes.c_uint32
         self.core.CGImageGetDataProvider.restype = ctypes.c_void_p
         self.core.CGDataProviderCopyData.restype = ctypes.c_void_p
         self.core.CFDataGetBytePtr.restype = ctypes.c_void_p
@@ -168,10 +170,6 @@ def grab(self, monitor):
         # type: (Dict[str, int]) -> ScreenShot
         """
         See :meth:`MSSBase.grab <mss.base.MSSBase.grab>` for full details.
-
-        When the monitor width is not divisible by 16, its width is reduced
-        to the previous number divisible by 16.  So we need to add extra
-        black pixels.
         """
 
         # Convert PIL bbox style
@@ -183,7 +181,13 @@ def grab(self, monitor):
                 'height': monitor[3] - monitor[1],
             }
 
-        rounded_width = int(math.ceil(monitor['width'] // 16) * 16)
+        # When the monitor width is not divisible by 16, extra padding
+        # is added by macOS in the form of black pixels, which results
+        # in a screenshot with shifted pixels.  To counter this, we
+        # round the width to the nearest integer divisible by 16, and
+        # we remove the extra width from the image after taking the
+        # screenshot.
+        rounded_width = math.ceil(monitor['width'] / 16) * 16
 
         rect = CGRect((monitor['left'], monitor['top']),
                       (rounded_width, monitor['height']))
@@ -193,6 +197,7 @@ def grab(self, monitor):
             raise ScreenShotError(
                 'CoreGraphics.CGWindowListCreateImage() failed.', locals())
 
+        width = int(self.core.CGImageGetWidth(image_ref))
         prov = self.core.CGImageGetDataProvider(image_ref)
         copy_data = self.core.CGDataProviderCopyData(prov)
         data_ref = self.core.CFDataGetBytePtr(copy_data)
@@ -203,24 +208,18 @@ def grab(self, monitor):
         self.core.CFRelease(copy_data)
 
         if rounded_width != monitor['width']:
-            data = self.resize(data, monitor)
+            data = self._crop_width(data, monitor, width)
 
         return self.cls_image(data, monitor)
 
     @staticmethod
-    def resize(data, monitor):
-        # type: (bytearray, Dict[str, int]) -> bytearray
-        """ Extend a 16 width-rounded screenshot to its original width. """
+    def _crop_width(image, monitor, width_to):
+        # type: (bytearray, Dict[str, int], int) -> bytearray
+        """ Cut off the pixels from an image buffer at a particular width. """
 
-        rounded_width = int(math.ceil(monitor['width'] // 16) * 16)
         cropped = bytearray()
-
         for row in range(monitor['height']):
-            start = row * rounded_width * 4
+            start = row * width_to * 4
             end = start + monitor['width'] * 4
-            cropped.extend(data[start:end])
-
-        if len(cropped) < monitor['width'] * monitor['width'] * 4:
-            cropped.extend(b'\00' * (monitor['width'] - rounded_width) * 4)
-
+            cropped.extend(image[start:end])
         return cropped
diff --git a/mss/screenshot.py b/mss/screenshot.py
@@ -53,10 +53,12 @@ def __array_interface__(self):
         See https://docs.scipy.org/doc/numpy/reference/arrays.interface.html
         """
 
-        return dict(version=3,
-                    shape=(self.height, self.width, 4),
-                    typestr='|u1',
-                    data=self.raw)
+        return {
+            'version': 3,
+            'shape': (self.height, self.width, 4),
+            'typestr': '|u1',
+            'data': self.raw,
+        }
 
     @classmethod
     def from_size(cls, data, width, height):
