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demo_affine_image.py
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demo_affine_image.py
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#!/usr/bin/env python
"""
For the backends that supports draw_image with optional affine
transform (e.g., agg, ps backend), the image of the output should
have its boundary matches the red rectangles.
"""
import numpy as np
import matplotlib.cm as cm
import matplotlib.mlab as mlab
import matplotlib.pyplot as plt
import matplotlib.transforms as mtransforms
def get_image():
delta = 0.25
x = y = np.arange(-3.0, 3.0, delta)
X, Y = np.meshgrid(x, y)
Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
Z = Z2-Z1 # difference of Gaussians
return Z
def imshow_affine(ax, z, *kl, **kwargs):
im = ax.imshow(z, *kl, **kwargs)
x1, x2, y1, y2 = im.get_extent()
im._image_skew_coordinate = (x2, y1)
return im
if 1:
# image rotation
ax1 = plt.subplot(121)
Z = get_image()
im1 = imshow_affine(ax1, Z, interpolation='nearest', cmap=cm.jet,
origin='lower',
extent=[-2, 4, -3, 2], clip_on=True)
trans_data2 = mtransforms.Affine2D().rotate_deg(30) + ax1.transData
im1.set_transform(trans_data2)
# display intended extent of the image
x1, x2, y1, y2 = im1.get_extent()
x3, y3 = x2, y1
ax1.plot([x1, x2, x2, x1, x1], [y1, y1, y2, y2, y1], "r--", lw=3,
transform=trans_data2)
ax1.set_xlim(-3, 5)
ax1.set_ylim(-4, 4)
# image skew
ax2 = plt.subplot(122)
im2 = ax2.imshow(Z, interpolation='nearest', cmap=cm.jet,
origin='lower',
extent=[-2, 4, -3, 2], clip_on=True)
im2._image_skew_coordinate = (3, -2)
plt.show()
#plt.savefig("demo_affine_image")