Add more transforms to affine image transform demo

examples/api/demo_affine_image.py

@@ -1,11 +1,10 @@
 """
-For the backends that supports draw_image with optional affine
+For the backends that support draw_image with optional affine
 transform (e.g., agg, ps backend), the image of the output should
-have its boundary matches the red rectangles.
+have its boundary match the dashed yellow rectangle.
 """
 
 import numpy as np
-import matplotlib.cm as cm
 import matplotlib.mlab as mlab
 import matplotlib.pyplot as plt
 import matplotlib.transforms as mtransforms
@@ -21,25 +20,37 @@ def get_image():
     return Z
 
 
-if 1:
+def do_plot(ax, Z, transform):
+    im = ax.imshow(Z, interpolation='none',
+                   origin='lower',
+                   extent=[-2, 4, -3, 2], clip_on=True)
+
+    trans_data = transform + ax.transData
+    im.set_transform(trans_data)
+
+    # display intended extent of the image
+    x1, x2, y1, y2 = im.get_extent()
+    ax.plot([x1, x2, x2, x1, x1], [y1, y1, y2, y2, y1], "y--",
+            transform=trans_data)
+    ax.set_xlim(-5, 5)
+    ax.set_ylim(-4, 4)
 
-    # image rotation
 
-    fig, ax1 = plt.subplots(1, 1)
+if 1:
+    fig, ((ax1, ax2), (ax3, ax4)) = plt.subplots(2, 2)
     Z = get_image()
-    im1 = ax1.imshow(Z, interpolation='none',
-                     origin='lower',
-                     extent=[-2, 4, -3, 2], clip_on=True)
 
-    trans_data2 = mtransforms.Affine2D().rotate_deg(30) + ax1.transData
-    im1.set_transform(trans_data2)
+    # image rotation
+    do_plot(ax1, Z, mtransforms.Affine2D().rotate_deg(30))
+
+    # image skew
+    do_plot(ax2, Z, mtransforms.Affine2D().skew_deg(30, 15))
 
-    # display intended extent of the image
-    x1, x2, y1, y2 = im1.get_extent()
-    x3, y3 = x2, y1
+    # scale and reflection
+    do_plot(ax3, Z, mtransforms.Affine2D().scale(-1, .5))
 
-    ax1.plot([x1, x2, x2, x1, x1], [y1, y1, y2, y2, y1], "--",
-             transform=trans_data2)
+    # everything and a translation
+    do_plot(ax4, Z, mtransforms.Affine2D().
+            rotate_deg(30).skew_deg(30, 15).scale(-1, .5).translate(.5, -1))
 
-    ax1.set_xlim(-3, 5)
-    ax1.set_ylim(-4, 4)
+    plt.show()