DOC: Move radon example to gallery.

doc/examples/plot_radon_transform.py

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+"""
+===============
+Radon transform
+===============
+
+The radon transform is a technique widely used in tomography to
+reconstruct an object from different projections. A projection is, for
+example, the scattering data obtained as the output of a tomographic
+scan.
+
+For more information see:
+
+  - http://en.wikipedia.org/wiki/Radon_transform
+  - http://www.clear.rice.edu/elec431/projects96/DSP/bpanalysis.html
+
+This script performs the radon transform, and reconstructs the
+input image based on the resulting sinogram.
+
+"""
+
+import matplotlib.pyplot as plt
+
+from scikits.image.io import imread
+from scikits.image import data_dir
+from scikits.image.transform import radon, iradon
+from scipy.ndimage import zoom
+
+image = imread(data_dir + "/phantom.png", as_grey=True)
+image = zoom(image, 0.4)
+
+plt.figure(figsize=(9, 8.5), dpi=75)
+
+plt.subplot(221)
+plt.title("Original");
+plt.imshow(image, cmap=plt.cm.Greys_r)
+
+plt.subplot(222)
+projections = radon(image, theta=[0, 45, 90])
+plt.plot(projections);
+plt.title("Projections at\n0, 45 and 90 degrees")
+plt.xlabel("Projection axis");
+plt.ylabel("Intensity");
+
+projections = radon(image)
+plt.subplot(223)
+plt.title("Radon transform\n(Sinogram)");
+plt.xlabel("Projection axis");
+plt.ylabel("Intensity");
+plt.imshow(projections)
+
+reconstruction = iradon(projections)
+plt.subplot(224)
+plt.title("Reconstruction\nfrom sinogram")
+plt.imshow(reconstruction, cmap=plt.cm.Greys_r)
+
+plt.subplots_adjust(hspace=0.4, wspace=0.5)
+plt.show()