def correlate2d(im1,im2, boundary='wrap', **kwargs):
"""
Cross-correlation of two images of arbitrary size. Returns an image
cropped to the largest of each dimension of the input images
Options
-------
return_fft - if true, return fft(im1)*fft(im2[::-1,::-1]), which is the power
spectral density
fftshift - if true, return the shifted psd so that the DC component is in
the center of the image
pad - Default on. Zero-pad image to the nearest 2^n
crop - Default on. Return an image of the size of the largest input image.
If the images are asymmetric in opposite directions, will return the largest
image in both directions.
boundary: str, optional
A flag indicating how to handle boundaries:
* 'fill' : set values outside the array boundary to fill_value
(default)
* 'wrap' : periodic boundary
WARNING: Normalization may be arbitrary if you use the PSD
"""
return convolve(np.conjugate(im1), im2[::-1, ::-1], normalize_kernel=False,
boundary=boundary, ignore_edge_zeros=False, **kwargs)
def smooth(image, kernelwidth=3, kerneltype='gaussian', trapslope=None,
silent=True, psf_pad=True, interp_nan=False, nwidths='max',
min_nwidths=6, return_kernel=False, normalize_kernel=np.sum,
downsample=False, downsample_factor=None, ignore_edge_zeros=False,
**kwargs):
"""
Returns a smoothed image using a gaussian, boxcar, or tophat kernel
Parameters
----------
kernelwidth:
width of kernel in pixels (see definitions below)
kerneltype:
gaussian, boxcar, or tophat.
For a gaussian, uses a gaussian with sigma = kernelwidth (in pixels)
out to [nwidths]-sigma
A boxcar is a kernelwidth x kernelwidth square
A tophat is a flat circle with radius = kernelwidth
psf_pad: [True]
will pad the input image to be the image size + PSF.
Slows things down but removes edge-wrapping effects (see convolve)
This option should be set to false if the edges of your image are
symmetric.
interp_nan: [False]
Will replace NaN points in an image with the
smoothed average of its neighbors (you can still simply ignore NaN
values by setting ignore_nan=True but leaving interp_nan=False)
silent: [True]
turn it off to get verbose statements about kernel types
return_kernel: [False]
If set to true, will return the kernel as the
second return value
nwidths: ['max']
number of kernel widths wide to make the kernel. Set to 'max' to
match the image shape, otherwise use any integer
min_nwidths: [6]
minimum number of gaussian widths to make the kernel
(the kernel will be larger than the image if the image size is <
min_widths*kernelsize)
normalize_kernel:
Should the kernel preserve the map sum (i.e. kernel.sum() = 1)
or the kernel peak (i.e. kernel.max() = 1) ? Must be a *function* that can
operate on a numpy array
downsample:
downsample after smoothing?
downsample_factor:
if None, default to kernelwidth
ignore_edge_zeros: bool
Ignore the zero-pad-created zeros. This will effectively decrease
the kernel area on the edges but will not re-normalize the kernel.
This parameter may result in 'edge-brightening' effects if you're using
a normalized kernel
Note that the kernel is forced to be even sized on each axis to assure no
offset when smoothing.
"""
if (kernelwidth*min_nwidths > image.shape[0] or kernelwidth*min_nwidths > image.shape[1]):
nwidths = min_nwidths
if (nwidths!='max'):# and kernelwidth*nwidths < image.shape[0] and kernelwidth*nwidths < image.shape[1]):
dimsize = np.ceil(kernelwidth*nwidths)
dimsize += dimsize % 2
yy,xx = np.indices([dimsize,dimsize])
szY,szX = dimsize,dimsize
else:
szY,szX = image.shape
szY += szY % 2
szX += szX % 2
yy,xx = np.indices([szY,szX])
shape = (szY,szX)
if not silent: print "Kernel size set to ",shape
kernel = make_kernel(shape, kernelwidth=kernelwidth, kerneltype=kerneltype,
normalize_kernel=normalize_kernel, trapslope=trapslope)
if not silent: print "Kernel of type %s normalized with %s has peak %g" % (kerneltype, normalize_kernel, kernel.max())
bad = (image != image)
temp = image.copy() # to preserve NaN values
# convolve does this already temp[bad] = 0
# kwargs parsing to avoid duplicate keyword passing
#if not kwargs.has_key('ignore_edge_zeros'): kwargs['ignore_edge_zeros']=True
if not kwargs.has_key('interpolate_nan'): kwargs['interpolate_nan']=interp_nan
# No need to normalize - normalization is dealt with in this code
temp = convolve(temp,kernel,psf_pad=psf_pad, normalize_kernel=False,
ignore_edge_zeros=ignore_edge_zeros, **kwargs)
if interp_nan is False: temp[bad] = image[bad]
if temp.shape != image.shape:
raise ValueError("Output image changed size; this is completely impossible.")
if downsample:
if downsample_factor is None: downsample_factor = kernelwidth
if return_kernel: return downsample_2d(temp,downsample_factor),downsample_2d(kernel,downsample_factor)
else: return downsample_2d(temp,downsample_factor)
else:
if return_kernel: return temp,kernel
else: return temp
def smooth(image, kernelwidth=3, kerneltype='gaussian', trapslope=None,
silent=True, psf_pad=True, interpolate_nan=False, nwidths='max',
min_nwidths=6, return_kernel=False, normalize_kernel=np.sum,
downsample=False, downsample_factor=None, ignore_edge_zeros=False,
use_fft=True,
**kwargs):
"""
Returns a smoothed image using a gaussian, boxcar, or tophat kernel
Parameters
----------
kernelwidth:
width of kernel in pixels (see definitions below)
kerneltype:
gaussian, boxcar, or tophat.
For a gaussian, uses a gaussian with sigma = kernelwidth (in pixels)
out to [nwidths]-sigma
A boxcar is a kernelwidth x kernelwidth square
A tophat is a flat circle with radius = kernelwidth
psf_pad: [True]
will pad the input image to be the image size + PSF.
Slows things down but removes edge-wrapping effects (see convolve)
This option should be set to false if the edges of your image are
symmetric.
interpolate_nan: [False]
Will replace NaN points in an image with the
smoothed average of its neighbors (you can still simply ignore NaN
values by setting ignore_nan=True but leaving interpolate_nan=False)
silent: [True]
turn it off to get verbose statements about kernel types
return_kernel: [False]
If set to true, will return the kernel as the
second return value
nwidths: ['max']
number of kernel widths wide to make the kernel. Set to 'max' to
match the image shape, otherwise use any integer
min_nwidths: [6]
minimum number of gaussian widths to make the kernel
(the kernel will be larger than the image if the image size is <
min_widths*kernelsize)
normalize_kernel:
Should the kernel preserve the map sum (i.e. kernel.sum() = 1)
or the kernel peak (i.e. kernel.max() = 1) ? Must be a *function* that can
operate on a numpy array
downsample:
downsample after smoothing?
downsample_factor:
if None, default to kernelwidth
ignore_edge_zeros: bool
Ignore the zero-pad-created zeros. This will effectively decrease
the kernel area on the edges but will not re-normalize the kernel.
This parameter may result in 'edge-brightening' effects if you're using
a normalized kernel
Note that the kernel is forced to be even sized on each axis to assure no
offset when smoothing.
"""
if (kernelwidth*min_nwidths > image.shape[0] or kernelwidth*min_nwidths > image.shape[1]):
nwidths = min_nwidths
if (nwidths!='max'):# and kernelwidth*nwidths < image.shape[0] and kernelwidth*nwidths < image.shape[1]):
dimsize = np.ceil(kernelwidth*nwidths)
dimsize += dimsize % 2
yy,xx = np.indices([dimsize,dimsize])
szY,szX = dimsize,dimsize
else:
szY,szX = image.shape
szY += szY % 2
szX += szX % 2
yy,xx = np.indices([szY,szX])
shape = (szY,szX)
if not silent: print "Kernel size set to ",shape
kernel = make_kernel(shape, kernelwidth=kernelwidth, kerneltype=kerneltype,
normalize_kernel=normalize_kernel, trapslope=trapslope)
if not silent: print "Kernel of type %s normalized with %s has peak %g" % (kerneltype, normalize_kernel, kernel.max())
bad = (image != image)
temp = image.copy() # to preserve NaN values
# convolve does this already temp[bad] = 0
# kwargs parsing to avoid duplicate keyword passing
#if not kwargs.has_key('ignore_edge_zeros'): kwargs['ignore_edge_zeros']=True
if not kwargs.has_key('interpolate_nan'): kwargs['interpolate_nan']=interpolate_nan
if use_fft:
# No need to normalize - normalization is dealt with in this code
temp = convolve(temp,kernel,psf_pad=psf_pad, normalize_kernel=False,
ignore_edge_zeros=ignore_edge_zeros, **kwargs)
else:
temp = convolve_cy(temp,kernel, **kwargs)
if interpolate_nan is False: temp[bad] = image[bad]
if temp.shape != image.shape:
raise ValueError("Output image changed size; this is completely impossible.")
if downsample:
if downsample_factor is None: downsample_factor = kernelwidth
if return_kernel: return downsample_2d(temp,downsample_factor),downsample_2d(kernel,downsample_factor)
else: return downsample_2d(temp,downsample_factor)
else:
if return_kernel: return temp,kernel
else: return temp
