MSS: Add ScreenShot.bgra property

Author: eruffaldi

mss/screenshot.py

@@ -126,6 +126,16 @@ def pixel(self, coord_x, coord_y):
         except IndexError:
             raise ScreenShotError('Pixel location out of range.', locals())
 
+    @property
+    def bgra(self):
+        # type: () -> bytes
+        """
+        Compute BGRA values from the BGRA raw pixels.
+
+        :return bytes: BGRA pixels.
+        """
+        return bytes(self.raw)
+
     @property
     def rgb(self):
         # type: () -> bytes