def subaperture_processing_phase_history(phase_array,
aperture_indices,
output_resolution,
dimension=0):
"""
Perform the sub-aperture processing on the given complex phase history data.
Parameters
----------
phase_array : numpy.ndarray
The complex array data. Dimension other than 2 is not supported.
aperture_indices : Tuple[int, int]
The start/stop indices for the subaperture processing.
output_resolution : int
The output resolution parameter.
dimension : int
The dimension along which to perform the sub-aperture processing. Must be
one of 0 or 1.
Returns
-------
numpy.ndarray
"""
phase_array = _validate_input(phase_array)
dimension = _validate_dimension(dimension)
if dimension == 0:
return ifft(phase_array[aperture_indices[0]:aperture_indices[1], :],
axis=0,
n=output_resolution)
else:
return ifft(phase_array[:, aperture_indices[0]:aperture_indices[1]],
axis=1,
n=output_resolution)
def _deweight_array(input_data, weight_array, oversample_rate, dimension):
"""
Uniformly weight complex SAR data along the given dimension.
Parameters
----------
input_data : numpy.ndarray
weight_array : numpy.ndarray
oversample_rate : int|float
dimension : int
Returns
-------
numpy.ndarray
"""
if weight_array is None:
# nothing to be done
return input_data
weight_size = round(input_data.shape[dimension]/oversample_rate)
if weight_array.ndim != 1:
raise ValueError('weight_array must be one dimensional.')
if weight_array.size != weight_size:
weight_array = scipy.signal.resample(weight_array, weight_size)
weight_ind_start = int_func(numpy.floor(0.5*(input_data.shape[dimension] - weight_size)))
weight_ind_end = weight_ind_start + weight_size
output_data = fftshift(fft(input_data, axis=dimension), axes=dimension)
if dimension == 0:
output_data[weight_ind_start:weight_ind_end, :] /= weight_array[:, numpy.newaxis]
else:
output_data[:, weight_ind_start:weight_ind_end] /= weight_array
return ifft(ifftshift(output_data, axes=dimension), axis=dimension)
def apply_weight_array(input_data,
weight_array,
oversample_rate,
dimension,
inverse=False):
"""
Apply the weight array along the given dimension.
Parameters
----------
input_data : numpy.ndarray
The complex data array to weight.
weight_array : numpy.ndarray
The weight array.
oversample_rate : int|float
The oversample rate.
dimension : int
Along which dimension to apply the weighting? Must be one of `{0, 1}`.
inverse : bool
If `True`, this divides the weight (i.e. de-weight), otherwise it multiplies.
Returns
-------
numpy.ndarray
"""
if not (isinstance(input_data, numpy.ndarray) and input_data.ndim == 2):
raise ValueError('The data array must be two-dimensional')
if weight_array is None:
# nothing to be done
return input_data
weight_array, weight_ind_start, weight_ind_end = determine_weight_array(
input_data.shape, weight_array, oversample_rate, dimension)
if inverse and numpy.any(weight_array == 0):
raise ValueError(
'inverse=True and the weight array contains some zero entries.')
output_data = fftshift(fft(input_data, axis=dimension), axes=dimension)
if dimension == 0:
if inverse:
output_data[weight_ind_start:
weight_ind_end, :] /= weight_array[:, numpy.newaxis]
else:
output_data[weight_ind_start:
weight_ind_end, :] *= weight_array[:, numpy.newaxis]
else:
if inverse:
output_data[:, weight_ind_start:weight_ind_end] /= weight_array
else:
output_data[:, weight_ind_start:weight_ind_end] *= weight_array
return ifft(ifftshift(output_data, axes=dimension), axis=dimension)
def csi_array(array, dimension=0, platform_direction='R', fill=1, filter_map=None):
"""
Creates a color subaperture array from a complex array.
.. Note: this ignores any potential sign issues for the fft and ifft, because
the results would be identical - fft followed by ifft versus ifft followed
by fft.
Parameters
----------
array : numpy.ndarray
The complex valued SAR data, assumed to be in the "image" domain.
Required to be two-dimensional.
dimension : int
The dimension over which to split the sub-aperture.
platform_direction : str
The (case insensitive) platform direction, required to be one of `('R', 'L')`.
fill : float
The fill factor. This will be ignored if `filter_map` is provided.
filter_map : None|numpy.ndarray
The RGB filter mapping. This is assumed constructed using :func:`filter_map_construction`.
Returns
-------
numpy.ndarray
"""
if not (isinstance(array, numpy.ndarray) and len(array.shape) == 2 and numpy.iscomplexobj(array)):
raise ValueError('array must be a two-dimensional numpy array of complex dtype')
dimension = int_func(dimension)
if dimension not in [0, 1]:
raise ValueError('dimension must be 0 or 1, got {}'.format(dimension))
if dimension == 0:
array = array.T
pdir_func = platform_direction.upper()[0]
if pdir_func not in ['R', 'L']:
raise ValueError('It is expected that pdir is one of "R" or "L". Got {}'.format(platform_direction))
# get our filter construction data
if filter_map is None:
fill = max(1.0, float(fill))
filter_map = filter_map_construction(array.shape[1]/fill)
if not (isinstance(filter_map, numpy.ndarray) and
filter_map.dtype.name in ['float32', 'float64'] and
filter_map.ndim == 2 and filter_map.shape[1] == 3):
raise ValueError('filter_map must be a N x 3 numpy array of float dtype.')
# move to phase history domain
ph_indices = int(numpy.floor(0.5*(array.shape[1] - filter_map.shape[0]))) + \
numpy.arange(filter_map.shape[0], dtype=numpy.int32)
ph0 = fftshift(ifft(numpy.cast[numpy.complex128](array), axis=1), axes=1)[:, ph_indices]
# construct the filtered workspace
# NB: processing is more efficient with color band in the first dimension
ph0_RGB = numpy.zeros((3, array.shape[0], filter_map.shape[0]), dtype=numpy.complex128)
for i in range(3):
ph0_RGB[i, :, :] = ph0*filter_map[:, i]
del ph0
# Shift phase history to avoid having zeropad in middle of filter, to alleviate
# the purple sidelobe artifact.
filter_shift = int(numpy.ceil(0.25*filter_map.shape[0]))
ph0_RGB[0, :] = numpy.roll(ph0_RGB[0, :], -filter_shift)
ph0_RGB[2, :] = numpy.roll(ph0_RGB[2, :], filter_shift)
# NB: the green band is already centered
# FFT back to the image domain
im0_RGB = fft(fftshift(ph0_RGB, axes=2), n=array.shape[1], axis=2)
del ph0_RGB
# Replace the intensity with the original image intensity to main full resolution
# (in intensity, but not in color).
scale_factor = numpy.abs(array)/numpy.abs(im0_RGB).max(axis=0)
im0_RGB = numpy.abs(im0_RGB)*scale_factor
# reorient image so that the color segment is in the final dimension
if dimension == 0:
im0_RGB = im0_RGB.transpose([2, 1, 0])
else:
im0_RGB = im0_RGB.transpose([1, 2, 0])
if pdir_func == 'R':
# reverse the color band order
im0_RGB = im0_RGB[:, :, ::-1]
return im0_RGB
