SF.net SVN: matplotlib:[6363] trunk/matplotlib/examples/pylab_examples/ text_rotation_relative_to_line.py

[<dmk...@us...>]

Revision: 6363
          http://matplotlib.svn.sourceforge.net/matplotlib/?rev=6363&view=rev
Author:   dmkaplan
Date:     2008-11-05 14:43:29 +0000 (Wed, 05 Nov 2008)

Log Message:
-----------
Adding a small script that demonstrates the utility of transform_angles method added in last
commit (from dmkaplan).

Added Paths:
-----------
    trunk/matplotlib/examples/pylab_examples/text_rotation_relative_to_line.py

Added: trunk/matplotlib/examples/pylab_examples/text_rotation_relative_to_line.py
===================================================================
--- trunk/matplotlib/examples/pylab_examples/text_rotation_relative_to_line.py	                        (rev 0)
+++ trunk/matplotlib/examples/pylab_examples/text_rotation_relative_to_line.py	2008-11-05 14:43:29 UTC (rev 6363)
@@ -0,0 +1,36 @@
+#!/usr/bin/env python
+"""
+Text objects in matplotlib are normally rotated with respect to the
+screen coordinate system (i.e., 45 degrees rotation plots text along a
+line that is inbetween horizontal and vertical no matter how the axes
+are changed).  However, at times one wants to rotate text with respect
+to something on the plot.  In this case, the correct angle won't be
+the angle of that object in the plot coordinate system, but the angle
+that that object APPEARS in the screen coordinate system.  This angle
+is found by transforming the angle from the plot to the screen
+coordinate system, as shown in the example below.
+"""
+from pylab import *
+
+# Plot diagonal line (45 degrees)
+h = plot( r_[:10], r_[:10] )
+
+# set limits so that it no longer looks on screen to be 45 degrees
+xlim([-10,20])
+
+# Locations to plot text
+l1 = array((1,1))
+l2 = array((5,5))
+
+# Rotate angle
+angle = 45
+trans_angle = gca().transData.transform_angles(array((45,)),
+                                               l2.reshape((1,2)))[0]
+
+# Plot text
+th1 = text(l1[0],l1[1],'text not rotated correctly',fontsize=16,
+           rotation=angle)
+th2 = text(l2[0],l2[1],'text not rotated correctly',fontsize=16,
+           rotation=trans_angle)
+
+show()


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