def do_gaussian_fit(scale, mu, sigma):
start = mu - 6 * sigma
stop = mu + 6 * sigma
step = (stop - start) / 1000
x = flex.double(frange(start, stop, step))
y = scale * flex.exp(-flex.pow2(x - mu) / (2 * sigma**2))
fit = curve_fitting.single_gaussian_fit(x, y)
assert approx_equal(fit.a, scale, 1e-4)
assert approx_equal(fit.b, mu, eps=1e-4)
assert approx_equal(fit.c, sigma, eps=1e-4)
def do_gaussian_fit(scale, mu, sigma): start = mu - 6 * sigma stop = mu + 6 * sigma step = (stop - start)/1000 x = flex.double(frange(start, stop, step)) y = scale * flex.exp(-flex.pow2(x - mu) / (2 * sigma**2)) fit = curve_fitting.single_gaussian_fit(x, y) assert approx_equal(fit.a, scale, 1e-4) assert approx_equal(fit.b, mu, eps=1e-4) assert approx_equal(fit.c, sigma, eps=1e-4)
def common_mode(self, img, stddev, mask):
"""The common_mode() function returns the mode of image stored in
the array pointed to by @p img. @p mask must be such that the @p
stddev at the selected pixels is greater than zero.
@param img 2D integer array of the image
@param stddev 2D integer array of the standard deviation of each
pixel in @p img
@param mask 2D Boolean array, @c True if the pixel is to be
included, @c False otherwise
@return Mode of the image, as a real number
"""
# Flatten the image and take out inactive pixels XXX because we
# cannot take means and medians of 2D arrays?
img_1d = img.as_1d().select(mask.as_1d()).as_double()
assert img_1d.size() > 0
if (self.common_mode_correction == "mean"):
# The common mode is approximated by the mean of the pixels with
# signal-to-noise ratio less than a given threshold. XXX Breaks
# if the selection is empty!
THRESHOLD_SNR = 2
img_snr = img_1d / stddev.as_double().as_1d().select(mask.as_1d())
return (flex.mean(img_1d.select(img_snr < THRESHOLD_SNR)))
elif (self.common_mode_correction == "median"):
return (flex.median(img_1d))
# Identify the common-mode correction as the peak histogram of the
# histogram of pixel values (the "standard" common-mode correction, as
# previously implemented in this class).
hist_min = -40
hist_max = 40
n_slots = 100
hist = flex.histogram(img_1d, hist_min, hist_max, n_slots=n_slots)
slots = hist.slots()
i = flex.max_index(slots)
common_mode = list(hist.slot_infos())[i].center()
if (self.common_mode_correction == "mode"):
return (common_mode)
# Determine the common-mode correction from the peak of a single
# Gaussian function fitted to the histogram.
from scitbx.math.curve_fitting import single_gaussian_fit
x = hist.slot_centers()
y = slots.as_double()
fit = single_gaussian_fit(x, y)
scale, mu, sigma = fit.a, fit.b, fit.c
self.logger.debug("fitted gaussian: mu=%.3f, sigma=%.3f" %(mu, sigma))
mode = common_mode
common_mode = mu
if abs(mode-common_mode) > 1000: common_mode = mode # XXX
self.logger.debug("delta common mode corrections: %.3f" %(mode-common_mode))
if 0 and abs(mode-common_mode) > 0:
#if 0 and skew > 0.5:
# view histogram and fitted gaussian
from numpy import exp
from matplotlib import pyplot
x_all = x
n, bins, patches = pyplot.hist(section_img.as_1d().as_numpy_array(), bins=n_slots, range=(hist_min, hist_max))
y_all = scale * flex.exp(-flex.pow2(x_all-mu) / (2 * sigma**2))
scale = slots[flex.max_index(slots)]
y_all *= scale/flex.max(y_all)
pyplot.plot(x_all, y_all)
pyplot.show()
return (common_mode)
