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plotting.py
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plotting.py
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import numpy as np
import matplotlib
matplotlib.use('Agg')
from matplotlib import pyplot as plt
# Plot image examples.
def plot_img(img, title=None):
plt.figure()
plt.imshow(img, interpolation='nearest')
if title is not None:
plt.title(title)
plt.axis('off')
plt.tight_layout()
def img_stretch(img):
img = img.astype(float)
img -= np.min(img)
img /= np.max(img)+1e-12
return img
def img_tile(imgs, aspect_ratio=1.0, tile_shape=None, border=1,
border_color=0, stretch=False):
''' Tile images in a grid.
If tile_shape is provided only as many images as specified in tile_shape
will be included in the output.
'''
# Prepare images
if stretch:
imgs = img_stretch(imgs)
imgs = np.array(imgs)
if imgs.ndim != 3 and imgs.ndim != 4:
raise ValueError('imgs has wrong number of dimensions.')
n_imgs = imgs.shape[0]
# Grid shape
img_shape = np.array(imgs.shape[1:3])
if tile_shape is None:
img_aspect_ratio = img_shape[1] / float(img_shape[0])
aspect_ratio *= img_aspect_ratio
tile_height = int(np.ceil(np.sqrt(n_imgs * aspect_ratio)))
tile_width = int(np.ceil(np.sqrt(n_imgs / aspect_ratio)))
grid_shape = np.array((tile_height, tile_width))
else:
assert len(tile_shape) == 2
grid_shape = np.array(tile_shape)
# Tile image shape
tile_img_shape = np.array(imgs.shape[1:])
tile_img_shape[:2] = (img_shape[:2] + border) * grid_shape[:2] - border
# Assemble tile image
tile_img = np.empty(tile_img_shape)
tile_img[:] = border_color
for i in range(grid_shape[0]):
for j in range(grid_shape[1]):
img_idx = j + i*grid_shape[1]
if img_idx >= n_imgs:
# No more images - stop filling out the grid.
break
img = imgs[img_idx]
yoff = (img_shape[0] + border) * i
xoff = (img_shape[1] + border) * j
tile_img[yoff:yoff+img_shape[0], xoff:xoff+img_shape[1], ...] = img
return tile_img
def conv_filter_tile(filters):
n_filters, n_channels, height, width = filters.shape
tile_shape = None
if n_channels == 3:
# Interpret 3 color channels as RGB
filters = np.transpose(filters, (0, 2, 3, 1))
else:
# Organize tile such that each row corresponds to a filter and the
# columns are the filter channels
tile_shape = (n_channels, n_filters)
filters = np.transpose(filters, (1, 0, 2, 3))
filters = np.resize(filters, (n_filters*n_channels, height, width))
filters = img_stretch(filters)
return img_tile(filters, tile_shape=tile_shape)
def scale_to_unit_interval(ndar, eps=1e-8):
""" Scales all values in the ndarray ndar to be between 0 and 1 """
ndar = ndar.copy()
ndar -= ndar.min()
ndar *= 1.0 / (ndar.max() + eps)
return ndar
def tile_raster_images(X, img_shape, tile_shape, tile_spacing=(0, 0),
scale_rows_to_unit_interval=True,
output_pixel_vals=True):
"""
Transform an array with one flattened image per row, into an array in
which images are reshaped and layed out like tiles on a floor.
This function is useful for visualizing datasets whose rows are images,
and also columns of matrices for transforming those rows
(such as the first layer of a neural net).
:type X: a 2-D ndarray or a tuple of 4 channels, elements of which can
be 2-D ndarrays or None;
:param X: a 2-D array in which every row is a flattened image.
:type img_shape: tuple; (height, width)
:param img_shape: the original shape of each image
:type tile_shape: tuple; (rows, cols)
:param tile_shape: the number of images to tile (rows, cols)
:param output_pixel_vals: if output should be pixel values (i.e. int8
values) or floats
:param scale_rows_to_unit_interval: if the values need to be scaled before
being plotted to [0,1] or not
:returns: array suitable for viewing as an image.
(See:`PIL.Image.fromarray`.)
:rtype: a 2-d array with same dtype as X.
"""
assert len(img_shape) == 2
assert len(tile_shape) == 2
assert len(tile_spacing) == 2
# The expression below can be re-written in a more C style as
# follows :
#
# out_shape = [0,0]
# out_shape[0] = (img_shape[0] + tile_spacing[0]) * tile_shape[0] -
# tile_spacing[0]
# out_shape[1] = (img_shape[1] + tile_spacing[1]) * tile_shape[1] -
# tile_spacing[1]
out_shape = [(ishp + tsp) * tshp - tsp for ishp, tshp, tsp
in zip(img_shape, tile_shape, tile_spacing)]
if isinstance(X, tuple):
assert len(X) == 4
# Create an output numpy ndarray to store the image
if output_pixel_vals:
out_array = np.zeros((out_shape[0], out_shape[1], 4), dtype='uint8')
else:
out_array = np.zeros((out_shape[0], out_shape[1], 4), dtype=X.dtype)
#colors default to 0, alpha defaults to 1 (opaque)
if output_pixel_vals:
channel_defaults = [0, 0, 0, 255]
else:
channel_defaults = [0., 0., 0., 1.]
for i in range(4):
if X[i] is None:
# if channel is None, fill it with zeros of the correct
# dtype
out_array[:, :, i] = np.zeros(out_shape,
dtype='uint8' if output_pixel_vals else out_array.dtype
) + channel_defaults[i]
else:
# use a recurrent call to compute the channel and store it
# in the output
out_array[:, :, i] = tile_raster_images(X[i], img_shape, tile_shape, tile_spacing, scale_rows_to_unit_interval, output_pixel_vals)
return out_array
else:
# if we are dealing with only one channel
H, W = img_shape
Hs, Ws = tile_spacing
# generate a matrix to store the output
out_array = np.zeros(out_shape, dtype='uint8' if output_pixel_vals else X.dtype)
for tile_row in range(tile_shape[0]):
for tile_col in range(tile_shape[1]):
if tile_row * tile_shape[1] + tile_col < X.shape[0]:
if scale_rows_to_unit_interval:
# if we should scale values to be between 0 and 1
# do this by calling the `scale_to_unit_interval`
# function
this_img = scale_to_unit_interval(X[tile_row * tile_shape[1] + tile_col].reshape(img_shape))
else:
this_img = X[tile_row * tile_shape[1] + tile_col].reshape(img_shape)
# add the slice to the corresponding position in the
# output array
out_array[
tile_row * (H+Hs): tile_row * (H + Hs) + H,
tile_col * (W+Ws): tile_col * (W + Ws) + W
] \
= this_img * (255 if output_pixel_vals else 1)
return out_array