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DOC: update view_as_blocks and gabors_from_lena example using comments from @stevanv (PR #138)
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@@ -7,20 +7,20 @@ Gabors / Primary Visual Cortex "Simple Cells" from Lena
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How to build a (bio-plausible) "sparse" dictionary (or 'codebook', or
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'filterbank') for e.g. image classification without any fancy math and
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with just standard python scientific librairies?
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with just standard python scientific libraries?
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Please find below a short answer ;-)
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This simple example shows how to get Gabor-like filters [1]_ using just
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the famous Lena image. Gabor filters are good approximations of the
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"Simple Cells" [2]_ receptive fields [3]_ found in the mammalian primary
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visual cortex (V1) (for details, see e.g. the Nobel-prize winning work of Hubel
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& Wiesel done in the 60s).
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visual cortex (V1) (for details, see e.g. the Nobel-prize winning work
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of Hubel & Wiesel done in the 60s [4]_ [5]_).
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Here we use McQueen's 'kmeans' algorithm [4]_, as a simple bio-plausible
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hebbian-like learning rule and we apply it (a) to patches of the
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original Lena image (retinal projection), and (b) to patches of an
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LGN-like [5]_ Lena image using a simple difference of gaussians (DoG)
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Here we use McQueen's 'kmeans' algorithm [6]_, as a simple biologically
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plausible hebbian-like learning rule and we apply it (a) to patches of
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the original Lena image (retinal projection), and (b) to patches of an
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LGN-like [7]_ Lena image using a simple difference of gaussians (DoG)
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approximation.
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Enjoy ;-) And keep in mind that getting Gabors on natural image patches
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@@ -31,39 +31,36 @@ is not rocket science.
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.. [3] http://en.wikipedia.org/wiki/Receptive_field
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.. [4] http://en.wikipedia.org/wiki/K-means_clustering
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.. [5] http://en.wikipedia.org/wiki/Lateral_geniculate_nucleus
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References
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----------
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D. H. Hubel and T. N. Wiesel Receptive Fields of Single Neurones in the
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Cat's Striate Cortex J. Physiol. pp. 574-591 (148) 1959
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D. H. Hubel and T. N. Wiesel Receptive Fields, Binocular Interaction and
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Functional Architecture in the Cat's Visual Cortex J. Physiol. 160 pp.
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106-154 1962
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.. [6] D. H. Hubel and T. N. Wiesel Receptive Fields of Single Neurones
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in the Cat's Striate Cortex J. Physiol. pp. 574-591 (148) 1959
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.. [7] D. H. Hubel and T. N. Wiesel Receptive Fields, Binocular
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Interaction and Functional Architecture in the Cat's Visual Cortex J.
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Physiol. 160 pp. 106-154 1962
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"""
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import numpy as np
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from scipy import misc
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from scipy.cluster.vq import kmeans2
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from scipy import ndimage as ndi
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import matplotlib.pyplot as plt
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from skimage import data
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from skimage import color
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from skimage.util.shape import view_as_windows
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from skimage.util.montage import montage2d
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from scipy import ndimage as ndi
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np.random.seed(42)
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patch_shape = 8, 8
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n_filters = 49
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lena = misc.lena() / 255.
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lena = color.rgb2gray(data.lena()) / 255.
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# -- filterbank1 on original Lena
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patches1 = view_as_windows(lena, patch_shape)
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patches1 = patches1.reshape(-1, patch_shape[0] * patch_shape[1])[::8]
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fb1, _ = kmeans2(patches1, n_filters, minit='points')
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fb1 = fb1.reshape((-1,) + patch_shape)
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fb1_montage = montage2d(fb1)
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fb1_montage = montage2d(fb1, rescale_intensity=True)
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# -- filterbank2 LGN-like Lena
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lena_dog = ndi.gaussian_filter(lena, .5) - ndi.gaussian_filter(lena, 1)
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@@ -71,7 +68,7 @@ patches2 = view_as_windows(lena_dog, patch_shape)
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patches2 = patches2.reshape(-1, patch_shape[0] * patch_shape[1])[::8]
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fb2, _ = kmeans2(patches2, n_filters, minit='points')
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fb2 = fb2.reshape((-1,) + patch_shape)
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fb2_montage = montage2d(fb2)
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fb2_montage = montage2d(fb2, rescale_intensity=True)
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# --
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plt.figure(figsize=(9, 3))
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@@ -3,25 +3,28 @@
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Block views on images/arrays
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============================
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This example illustrates the use of `view_as_blocks` from `skimage.util.shape`.
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Block views can be incredibly useful when one wants to perform local operations
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on non-overlapping image patches.
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This example illustrates the use of `view_as_blocks` from
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`skimage.util.shape`. Block views can be incredibly useful when one
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wants to perform local operations on non-overlapping image patches.
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We use `lena` from `scipy.misc` and virtually 'slice' it into square blocks.
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Then, on each block, we either pool the mean, the max or the median value of
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that block. The results are displayed altogether, along with a 'classic'
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`bicubic` rescaling of the original `lena` image.
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We use `lena` from `skimage.data` and virtually 'slice' it into square
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blocks. Then, on each block, we either pool the mean, the max or the
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median value of that block. The results are displayed altogether, along
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with a 'classic' `bicubic` rescaling of the original `lena` image.
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"""
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import numpy as np
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from scipy.misc import lena, imresize
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from scipy.misc import imresize
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from matplotlib import pyplot as plt
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import matplotlib.cm as cm
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from skimage import data
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from skimage import color
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from skimage.util.shape import view_as_blocks
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# -- get `lena` from scipy in grayscale
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l = lena()
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# -- get `lena` from skimage.data in grayscale
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l = color.rgb2gray(data.lena()) / 255.
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# -- size of blocks
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block_shape = (4, 4)
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@@ -43,7 +46,7 @@ median_view = np.median(flatten_view, axis=2)
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plt.figure(figsize=(10, 10))
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plt.subplot(221)
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plt.title("Original rescaled\n in bicubic mode");
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plt.title("Original rescaled\n in bicubic mode")
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l_resized = imresize(l, view.shape[:2], interp='bicubic')
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plt.imshow(l_resized, cmap=cm.Greys_r)
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@@ -52,7 +55,7 @@ plt.title("Block view with\n local mean pooling")
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plt.imshow(mean_view, cmap=cm.Greys_r)
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plt.subplot(223)
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plt.title("Block view with\n local max pooling");
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plt.title("Block view with\n local max pooling")
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plt.imshow(max_view, cmap=cm.Greys_r)
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plt.subplot(224)
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