ps: Fix anchoring of rotated usetex text

In PostScript, usetex text is anchored to the bottom left for
replacement by psfrag, while in Matplotlib, text is placed by the
baseline usually. So PostScript subtracts the text depth from the y
position, but for rotated text, this subtraction should also be in a
rotated direction.

Author: QuLogic

lib/matplotlib/backends/backend_ps.py

@@ -588,8 +588,10 @@ def draw_tex(self, gc, x, y, s, prop, angle, *, mtext=None):
         s = fontcmd % s
         tex = r'\color[rgb]{%s} %s' % (color, s)
 
-        # Stick to the bottom alignment.
-        pos = _nums_to_str(x, y-bl)
+        # Stick to bottom-left alignment, so subtract descent from the text-normal
+        # direction since text is normally positioned by its baseline.
+        rangle = np.radians(angle + 90)
+        pos = _nums_to_str(x - bl * np.cos(rangle), y - bl * np.sin(rangle))
         self.psfrag.append(
             r'\psfrag{%s}[bl][bl][1][%f]{\fontsize{%f}{%f}%s}' % (
                 thetext, angle, fontsize, fontsize*1.25, tex))