def RandomImagePatches(iterable, imagecols, pshape, npatches):
"""
samples >> RandomImagePatches(imagecols, shape, npatches)
Extract patches at random locations from images.
>>> import numpy as np
>>> np.random.seed(0) # just to ensure stable doctest
>>> img = np.reshape(np.arange(30), (5, 6))
>>> samples = [(img, 0)]
>>> getpatches = RandomImagePatches(0, (2, 3), 3)
>>> for (p, l) in samples >> getpatches:
... print(p.tolist(), l)
[[7, 8, 9], [13, 14, 15]] 0
[[8, 9, 10], [14, 15, 16]] 0
[[8, 9, 10], [14, 15, 16]] 0
:param iterable iterable: Samples with images
:param int|tuple imagecols: Indices of sample columns that contain
images, where patches are extracted from.
Images must be numpy arrays of shape h,w,c or h,w
:param tuple shape: Shape of patch (h,w)
:param int npatches: Number of patches to extract (per image)
:return: Iterator over samples where images are replaced by patches.
:rtype: generator
"""
imagecols = as_tuple(imagecols)
for sample in iterable:
image = sample[imagecols[0]]
hi, wi = image.shape[:2]
hs2, ws2 = pshape[0] // 2 + 1, pshape[1] // 2 + 1
rr = np.random.randint(hs2, hi - hs2, npatches)
cc = np.random.randint(ws2, wi - ws2, npatches)
for r, c in zip(rr, cc):
yield ut.col_map(sample, imagecols, ni.extract_patch, pshape, r, c)
def RegularImagePatches(iterable, imagecols, pshape, stride):
"""
samples >> RegularImagePatches(imagecols, shape, stride)
Extract patches in a regular grid from images.
>>> import numpy as np
>>> img = np.reshape(np.arange(12), (3, 4))
>>> samples = [(img, 0)]
>>> getpatches = RegularImagePatches(0, (2, 2), 2)
>>> for p in samples >> getpatches:
... print(p)
(array([[0, 1],
[4, 5]]), 0)
(array([[2, 3],
[6, 7]]), 0)
:param iterable iterable: Samples with images
:param int|tuple imagecols: Indices of sample columns that contain
images, where patches are extracted from.
Images must be numpy arrays of shape h,w,c or h,w
:param tuple shape: Shape of patch (h,w)
:param int stride: Step size of grid patches are extracted from
:return: Iterator over samples where images are replaced by patches.
:rtype: generator
"""
colset = as_set(imagecols)
for sample in iterable:
patch_iters = ut.col_map(sample, imagecols, ni.patch_iter, pshape,
stride)
while True:
patched = []
for i, p in enumerate(patch_iters):
try:
patched.append(next(p) if i in colset else p)
except StopIteration:
pass
if len(patched) == len(sample):
yield tuple(patched)
else:
break # one or all patch iterators are depleted
def test_col_map():
sample = (1, 2, 3)
add_n = lambda x, n: x + n
assert util.col_map(sample, 1, add_n, 10) == (1, 12, 3)
assert util.col_map(sample, (0, 2), add_n, 10) == (11, 2, 13)
