Add skew() and skew_deg() to Affine2D.

dopplershift · dopplershift · commit c5cdcbf34a77 · 2014-03-09T20:56:28.000-06:00
These set up skew transforms, which can be viewed as indpendantly
rotating the X and Y axes.
diff --git a/lib/matplotlib/transforms.py b/lib/matplotlib/transforms.py
@@ -1873,6 +1873,39 @@ def scale(self, sx, sy=None):
         self.invalidate()
         return self
 
+    def skew(self, xAxisRot, yAxisRot):
+        """
+        Adds a skew in place.
+
+        *xAxisRot* and *yAxisRot* are the rotations of the *x*- and
+        *y*-axes, respectively, in radians.
+
+        Returns *self*, so this method can easily be chained with more
+        calls to :meth:`rotate`, :meth:`rotate_deg`, :meth:`translate`
+        and :meth:`scale`.
+        """
+        rotX = np.tan(xAxisRot)
+        rotY = np.tan(yAxisRot)
+        skew_mtx = np.array(
+                [[1.0, rotY, 0.0], [rotX, 1.0, 0.0], [0.0, 0.0, 1.0]],
+                np.float_)
+        self._mtx = np.dot(skew_mtx, self._mtx)
+        self.invalidate()
+        return self
+
+    def skew_deg(self, xAxisRot, yAxisRot):
+        """
+        Adds a skew in place.
+
+        *xAxisRot* and *yAxisRot* are the rotations of the *x*- and
+        *y*-axes, respectively, in degrees.
+
+        Returns *self*, so this method can easily be chained with more
+        calls to :meth:`rotate`, :meth:`rotate_deg`, :meth:`translate`
+        and :meth:`scale`.
+        """
+        return self.skew(np.deg2rad(xAxisRot), np.deg2rad(yAxisRot))
+
     def _get_is_separable(self):
         mtx = self.get_matrix()
         return mtx[0, 1] == 0.0 and mtx[1, 0] == 0.0
