def positive_arctan(x,y, htype = 'deg'):
"""
Calculate positive angle (0°-360° or 0 - 2*pi rad.) from x and y.
Args:
:x:
| ndarray of x-coordinates
:y:
| ndarray of y-coordinates
:htype:
| 'deg' or 'rad', optional
| - 'deg': hue angle between 0° and 360°
| - 'rad': hue angle between 0 and 2pi radians
Returns:
:returns:
| ndarray of positive angles.
"""
if htype == 'deg':
r2d = 180.0/np.pi
h360 = 360.0
else:
r2d = 1.0
h360 = 2.0*np.pi
h = np.atleast_1d((np.arctan2(y,x)*r2d))
h[np.where(h<0)] = h[np.where(h<0)] + h360
return h
def cart2spher(x, y, z, deg=True):
"""
Convert cartesian to spherical coordinates.
Args:
:x, y, z:
| tuple of floats, ints or ndarrays
| Cartesian coordinates
Returns:
:theta:
| Float, int or ndarray
| Angle with positive z-axis.
:phi:
| Float, int or ndarray
| Angle around positive z-axis starting from x-axis.
:r:
| 1, optional
| Float, int or ndarray
| radius
"""
r = np.sqrt(x * x + y * y + z * z)
phi = np.arctan2(y, x)
phi[phi < 0.] = phi[phi < 0.] + 2 * np.pi
zdr = z / r
zdr[zdr > 1.] = 1.
zdr[zdr < -1.] = -1
theta = np.arccos(zdr)
if deg == True:
theta = theta * 180 / np.pi
phi = phi * 180 / np.pi
return theta, phi, r
def positive_arctan(x, y, htype='deg'):
if htype == 'deg':
r2d = 180.0 / np.pi
h360 = 360.0
else:
r2d = 1.0
h360 = 2.0 * np.pi
h = np.atleast_1d((np.arctan2(y, x) * r2d))
h[np.where(h < 0)] = h[np.where(h < 0)] + h360
return h
def fit_ellipse(xy):
"""
Fit an ellipse to supplied data points.
Args:
:xy:
| coordinates of points to fit (Nx2 array)
Returns:
:v:
| vector with ellipse parameters [Rmax,Rmin, xc,yc, theta]
"""
# remove centroid:
center = xy.mean(axis=0)
xy = xy - center
# Fit ellipse:
x, y = xy[:, 0:1], xy[:, 1:2]
D = np.hstack((x * x, x * y, y * y, x, y, np.ones_like(x)))
S, C = np.dot(D.T, D), np.zeros([6, 6])
C[0, 2], C[2, 0], C[1, 1] = 2, 2, -1
U, s, V = np.linalg.svd(np.dot(np.linalg.inv(S), C))
e = U[:, 0]
# get ellipse axis lengths, center and orientation:
b, c, d, f, g, a = e[1] / 2, e[2], e[3] / 2, e[4] / 2, e[5], e[0]
# get ellipse center:
num = b * b - a * c
xc = ((c * d - b * f) / num) + center[0]
yc = ((a * f - b * d) / num) + center[1]
# get ellipse orientation:
theta = np.arctan2(np.array(2 * b), np.array((a - c))) / 2
# axis lengths:
up = 2 * (a * f * f + c * d * d + g * b * b - 2 * b * d * f - a * c * g)
down1 = (b * b - a * c) * ((c - a) * np.sqrt(1 + 4 * b * b / ((a - c) *
(a - c))) -
(c + a))
down2 = (b * b - a * c) * ((a - c) * np.sqrt(1 + 4 * b * b / ((a - c) *
(a - c))) -
(c + a))
a, b = np.sqrt(up / down1), np.sqrt(up / down2)
# assert that a is the major axis (otherwise swap and correct angle)
if (b > a):
b, a = a, b
# ensure the angle is betwen 0 and 2*pi
theta = fmod(theta, 2.0 * np.pi)
return np.hstack((a, b, xc, yc, theta))
def cik_to_v(cik, xyc=None, inverse=False):
"""
Calculate v-format ellipse descriptor from 2x2 'covariance matrix'^-1 cik
Args:
:cik:
| 'Nx2x2' (covariance matrix)^-1
:inverse:
| If True: input is inverse of cik.
Returns:
:v:
| (Nx5) np.ndarray
| ellipse parameters [Rmax,Rmin,xc,yc,theta]
Notes:
| cik is not actually the inverse covariance matrix,
| only for a Gaussian or normal distribution!
"""
if cik.ndim < 3:
cik = cik[None, ...]
if inverse == True:
for i in range(cik.shape[0]):
cik[i, :, :] = np.linalg.inv(cik[i, :, :])
g11 = cik[:, 0, 0]
g22 = cik[:, 1, 1]
g12 = cik[:, 0, 1]
theta = 0.5 * np.arctan2(2 * g12, (g11 - g22)) + (np.pi / 2) * (g12 < 0)
#theta = theta2 + (np.pi/2)*(g12<0)
#theta2 = theta
cottheta = np.cos(theta) / np.sin(theta) #np.cot(theta)
cottheta[np.isinf(cottheta)] = 0
a = 1 / np.sqrt((g22 + g12 * cottheta))
b = 1 / np.sqrt((g11 - g12 * cottheta))
# ensure largest ellipse axis is first (correct angle):
c = b > a
a[c], b[c], theta[c] = b[c], a[c], theta[c] + np.pi / 2
v = np.vstack((a, b, np.zeros(a.shape), np.zeros(a.shape), theta)).T
# add center coordinates:
if xyc is not None:
v[:, 2:4] = xyc
return v
def get_tpr(self, *args):
if len(args) > 0:
x, y, z = args
else:
x, y, z = self.x, self.y, self.z
r = np.sqrt(x * x + y * y + z * z)
zdr = np.asarray(z / r)
zdr[zdr > 1.0] = 1.0
zdr[zdr < -1.0] = -1.0
theta = np.arccos(z / r)
phi = np.arctan2(y, x)
phi[phi < 0.0] = phi[phi < 0.0] + 2 * np.pi
phi[r < self._TINY] = 0.0
theta[r < self._TINY] = 0.0
return theta, phi, r
def cik_to_v(cik, xyc=None, inverse=False):
"""
Calculate v-format ellipse descriptor from 2x2 'covariance matrix'^-1 cik
Args:
:cik:
'2x2xN' (covariance matrix)^-1
Returns:
:v:
| (Nx5) np.ndarray
| ellipse parameters [Rmax,Rmin,xc,yc,theta]
Notes:
| cik is not actually the inverse covariance matrix,
| only for a Gaussian or normal distribution!
"""
if inverse == True:
for i in np.arange(cik.shape[0]):
cik[i, :, :] = np.linalg.inv(cik[i, :, :])
g11 = cik[:, 0, 0]
g22 = cik[:, 1, 1]
g12 = cik[:, 0, 1]
theta2 = 1 / 2 * np.arctan2(2 * g12, (g11 - g22))
theta = theta2 + (np.pi / 2) * (g12 < 0)
theta2 = theta
cottheta = np.cos(theta) / np.sin(theta) #np.cot(theta)
cottheta[np.isinf(cottheta)] = 0
a = 1 / np.sqrt((g22 + g12 * cottheta))
b = 1 / np.sqrt((g11 - g12 * cottheta))
v = np.vstack((a, b, np.zeros(a.shape), np.zeros(a.shape), theta)).T
# add center coordinates:
if xyc is not None:
v[:, 2:4] = xyc
return v
def get_poly_model(jabt, jabr, modeltype = _VF_MODEL_TYPE):
"""
Setup base color shift model (delta_a, delta_b),
determine model parameters and accuracy.
| Calculates a base color shift (delta) from the ref. chromaticity ar, br.
Args:
:jabt:
| ndarray with jab color coordinates under the test SPD.
:jabr:
| ndarray with jab color coordinates under the reference SPD.
:modeltype:
| _VF_MODEL_TYPE or 'M6' or 'M5', optional
| Specifies degree 5 or degree 6 polynomial model in ab-coordinates.
(see notes below)
Returns:
:returns:
| (poly_model,
| pmodel,
| dab_model,
| dab_res,
| dCHoverC_res,
| dab_std,
| dCHoverC_std)
|
| :poly_model: function handle to model
| :pmodel: ndarray with model parameters
| :dab_model: ndarray with ab model predictions from ar, br.
| :dab_res: ndarray with residuals between 'da,db' of samples and
| 'da,db' predicted by the model.
| :dCHoverC_res: ndarray with residuals between 'dCoverC,dH'
| of samples and 'dCoverC,dH' predicted by the model.
| Note: dCoverC = (Ct - Cr)/Cr and dH = ht - hr
| (predicted from model, see notes below)
| :dab_std: ndarray with std of :dab_res:
| :dCHoverC_std: ndarray with std of :dCHoverC_res:
Notes:
1. Model types:
| poly5_model = lambda a,b,p: p[0]*a + p[1]*b + p[2]*(a**2) + p[3]*a*b + p[4]*(b**2)
| poly6_model = lambda a,b,p: p[0] + p[1]*a + p[2]*b + p[3]*(a**2) + p[4]*a*b + p[5]*(b**2)
2. Calculation of dCoverC and dH:
| dCoverC = (np.cos(hr)*da + np.sin(hr)*db)/Cr
| dHoverC = (np.cos(hr)*db - np.sin(hr)*da)/Cr
"""
at = jabt[...,1]
bt = jabt[...,2]
ar = jabr[...,1]
br = jabr[...,2]
# A. Calculate da, db:
da = at - ar
db = bt - br
# B.1 Calculate model matrix:
# 5-parameter model:
M5 = np.array([[np.sum(ar*ar), np.sum(ar*br), np.sum(ar*ar**2),np.sum(ar*ar*br),np.sum(ar*br**2)],
[np.sum(br*ar), np.sum(br*br), np.sum(br*ar**2),np.sum(br*ar*br),np.sum(br*br**2)],
[np.sum((ar**2)*ar), np.sum((ar**2)*br), np.sum((ar**2)*ar**2),np.sum((ar**2)*ar*br),np.sum((ar**2)*br**2)],
[np.sum(ar*br*ar), np.sum(ar*br*br), np.sum(ar*br*ar**2),np.sum(ar*br*ar*br),np.sum(ar*br*br**2)],
[np.sum((br**2)*ar), np.sum((br**2)*br), np.sum((br**2)*ar**2),np.sum((br**2)*ar*br),np.sum((br**2)*br**2)]])
#6-parameters model
M6 = np.array([[ar.size,np.sum(1.0*ar), np.sum(1.0*br), np.sum(1.0*ar**2),np.sum(1.0*ar*br),np.sum(1.0*br**2)],
[np.sum(ar*1.0),np.sum(ar*ar), np.sum(ar*br), np.sum(ar*ar**2),np.sum(ar*ar*br),np.sum(ar*br**2)],
[np.sum(br*1.0),np.sum(br*ar), np.sum(br*br), np.sum(br*ar**2),np.sum(br*ar*br),np.sum(br*br**2)],
[np.sum((ar**2)*1.0),np.sum((ar**2)*ar), np.sum((ar**2)*br), np.sum((ar**2)*ar**2),np.sum((ar**2)*ar*br),np.sum((ar**2)*br**2)],
[np.sum(ar*br*1.0),np.sum(ar*br*ar), np.sum(ar*br*br), np.sum(ar*br*ar**2),np.sum(ar*br*ar*br),np.sum(ar*br*br**2)],
[np.sum((br**2)*1.0),np.sum((br**2)*ar), np.sum((br**2)*br), np.sum((br**2)*ar**2),np.sum((br**2)*ar*br),np.sum((br**2)*br**2)]])
# B.2 Define model function:
poly5_model = lambda a,b,p: p[0]*a + p[1]*b + p[2]*(a**2) + p[3]*a*b + p[4]*(b**2)
poly6_model = lambda a,b,p: p[0] + p[1]*a + p[2]*b + p[3]*(a**2) + p[4]*a*b + p[5]*(b**2)
if modeltype == 'M5':
M = M5
poly_model = poly5_model
else:
M = M6
poly_model = poly6_model
M = np.linalg.inv(M)
# C.1 Data a,b analysis output:
if modeltype == 'M5':
da_model_parameters = np.dot(M, np.array([np.sum(da*ar), np.sum(da*br), np.sum(da*ar**2),np.sum(da*ar*br),np.sum(da*br**2)]))
db_model_parameters = np.dot(M, np.array([np.sum(db*ar), np.sum(db*br), np.sum(db*ar**2),np.sum(db*ar*br),np.sum(db*br**2)]))
else:
da_model_parameters = np.dot(M, np.array([np.sum(da*1.0),np.sum(da*ar), np.sum(da*br), np.sum(da*ar**2),np.sum(da*ar*br),np.sum(da*br**2)]))
db_model_parameters = np.dot(M, np.array([np.sum(db*1.0),np.sum(db*ar), np.sum(db*br), np.sum(db*ar**2),np.sum(db*ar*br),np.sum(db*br**2)]))
pmodel = np.vstack((da_model_parameters,db_model_parameters))
# D.1 Calculate model da, db:
da_model = poly_model(ar,br,pmodel[0])
db_model = poly_model(ar,br,pmodel[1])
dab_model = np.hstack((da_model,db_model))
# D.2 Calculate residuals for da & db:
da_res = da - da_model
db_res = db - db_model
dab_res = np.hstack((da_res,db_res))
dab_std = np.vstack((np.std(da_res,axis=0),np.std(db_res,axis=0)))
# E Calculate href, Cref:
href = np.arctan2(br,ar)
Cref = (ar**2 + br**2)**0.5
# F Calculate dC/C, dH/C for data and model and calculate residuals:
dCoverC = (np.cos(href)*da + np.sin(href)*db)/Cref
dHoverC = (np.cos(href)*db - np.sin(href)*da)/Cref
dCoverC_model = (np.cos(href)*da_model + np.sin(href)*db_model)/Cref
dHoverC_model = (np.cos(href)*db_model - np.sin(href)*da_model)/Cref
dCoverC_res = dCoverC - dCoverC_model
dHoverC_res = dHoverC - dHoverC_model
dCHoverC_std = np.vstack((np.std(dCoverC_res,axis = 0),np.std(dHoverC_res,axis = 0)))
dCHoverC_res = np.hstack((href,dCoverC_res,dHoverC_res))
return poly_model, pmodel, dab_model, dab_res, dCHoverC_res, dab_std, dCHoverC_std
def spd_to_ies_tm30_metrics(SPD, cri_type = None, \
hbins = 16, start_hue = 0.0,\
scalef = 100, \
vf_model_type = _VF_MODEL_TYPE, \
vf_pcolorshift = _VF_PCOLORSHIFT,\
scale_vf_chroma_to_sample_chroma = False):
"""
Calculates IES TM30 metrics from spectral data.
Args:
:data:
| numpy.ndarray with spectral data
:cri_type:
| None, optional
| If None: defaults to cri_type = 'iesrf'.
| Not none values of :hbins:, :start_hue: and :scalef: overwrite
input in cri_type['rg_pars']
:hbins:
| None or numpy.ndarray with sorted hue bin centers (°), optional
:start_hue:
| None, optional
:scalef:
| None, optional
| Scale factor for reference circle.
:vf_pcolorshift:
| _VF_PCOLORSHIFT or user defined dict, optional
| The polynomial models of degree 5 and 6 can be fully specified or
summarized by the model parameters themselved OR by calculating the
dCoverC and dH at resp. 5 and 6 hues. :VF_pcolorshift: specifies
these hues and chroma level.
:scale_vf_chroma_to_sample_chroma:
| False, optional
| Scale chroma of reference and test vf fields such that average of
binned reference chroma equals that of the binned sample chroma
before calculating hue bin metrics.
Returns:
:data:
| dict with color rendering data:
| - 'SPD' : ndarray test SPDs
| - 'bjabt': ndarray with binned jab data under test SPDs
| - 'bjabr': ndarray with binned jab data under reference SPDs
| - 'cct' : ndarray with CCT of test SPD
| - 'duv' : ndarray with distance to blackbody locus of test SPD
| - 'Rf' : ndarray with general color fidelity indices
| - 'Rg' : ndarray with gamut area indices
| - 'Rfi' : ndarray with specific color fidelity indices
| - 'Rfhi' : ndarray with local (hue binned) fidelity indices
| - 'Rcshi': ndarray with local chroma shifts indices
| - 'Rhshi': ndarray with local hue shifts indices
| - 'Rt' : ndarray with general metameric uncertainty index Rt
| - 'Rti' : ndarray with specific metameric uncertainty indices Rti
| - 'Rfhi_vf' : ndarray with local (hue binned) fidelity indices
| obtained from VF model predictions at color space
| pixel coordinates
| - 'Rcshi_vf': ndarray with local chroma shifts indices
| (same as above)
| - 'Rhshi_vf': ndarray with local hue shifts indices
| (same as above)
"""
if cri_type is None:
cri_type = 'iesrf'
#Calculate color rendering measures for SPDs in data:
out = 'Rf,Rg,cct,duv,Rfi,jabt,jabr,Rfhi,Rcshi,Rhshi,cri_type'
if isinstance(cri_type, str): # get dict
cri_type = _CRI_DEFAULTS[cri_type].copy()
if hbins is not None:
cri_type['rg_pars']['nhbins'] = hbins
if start_hue is not None:
cri_type['rg_pars']['start_hue'] = start_hue
if scalef is not None:
cri_type['rg_pars']['normalized_chroma_ref'] = scalef
Rf, Rg, cct, duv, Rfi, jabt, jabr, Rfhi, Rcshi, Rhshi, cri_type = spd_to_cri(
SPD, cri_type=cri_type, out=out)
rg_pars = cri_type['rg_pars']
#Calculate Metameric uncertainty and base color shifts:
dataVF = VF_colorshift_model(SPD,
cri_type=cri_type,
model_type=vf_model_type,
cspace=cri_type['cspace'],
sampleset=eval(cri_type['sampleset']),
pool=False,
pcolorshift=vf_pcolorshift,
vfcolor=0)
Rf_ = np.array([dataVF[i]['metrics']['Rf'] for i in range(len(dataVF))]).T
Rt = np.array([dataVF[i]['metrics']['Rt'] for i in range(len(dataVF))]).T
Rti = np.array([dataVF[i]['metrics']['Rti']
for i in range(len(dataVF))][0])
# Get normalized and sliced sample data for plotting:
rg_pars = cri_type['rg_pars']
nhbins, normalize_gamut, normalized_chroma_ref, start_hue = [
rg_pars[x] for x in sorted(rg_pars.keys())
]
normalized_chroma_ref = scalef
# np.sqrt((jabr[...,1]**2 + jabr[...,2]**2)).mean(axis = 0).mean()
if scale_vf_chroma_to_sample_chroma == True:
normalize_gamut = False
bjabt, bjabr = gamut_slicer(
jabt,
jabr,
out='jabt,jabr',
nhbins=nhbins,
start_hue=start_hue,
normalize_gamut=normalize_gamut,
normalized_chroma_ref=normalized_chroma_ref,
close_gamut=True)
Cr_s = (np.sqrt(bjabr[:-1, ..., 1]**2 + bjabr[:-1, ..., 2]**2)).mean(
axis=0) # for rescaling vector field average reference chroma
normalize_gamut = True #(for plotting)
bjabt, bjabr = gamut_slicer(jabt,
jabr,
out='jabt,jabr',
nhbins=nhbins,
start_hue=start_hue,
normalize_gamut=normalize_gamut,
normalized_chroma_ref=normalized_chroma_ref,
close_gamut=True)
Rfhi_vf = np.empty(Rfhi.shape)
Rcshi_vf = np.empty(Rcshi.shape)
Rhshi_vf = np.empty(Rhshi.shape)
for i in range(cct.shape[0]):
# Get normalized and sliced VF data for hue specific metrics:
vfjabt = np.hstack(
(np.ones(dataVF[i]['fielddata']['vectorfield']['axt'].shape),
dataVF[i]['fielddata']['vectorfield']['axt'],
dataVF[i]['fielddata']['vectorfield']['bxt']))
vfjabr = np.hstack(
(np.ones(dataVF[i]['fielddata']['vectorfield']['axr'].shape),
dataVF[i]['fielddata']['vectorfield']['axr'],
dataVF[i]['fielddata']['vectorfield']['bxr']))
nhbins, normalize_gamut, normalized_chroma_ref, start_hue = [
rg_pars[x] for x in sorted(rg_pars.keys())
]
vfbjabt, vfbjabr, vfbDEi = gamut_slicer(
vfjabt,
vfjabr,
out='jabt,jabr,DEi',
nhbins=nhbins,
start_hue=start_hue,
normalize_gamut=normalize_gamut,
normalized_chroma_ref=normalized_chroma_ref,
close_gamut=False)
if scale_vf_chroma_to_sample_chroma == True:
#rescale vfbjabt and vfbjabr to same chroma level as bjabr.
Cr_vfb = np.sqrt(vfbjabr[..., 1]**2 + vfbjabr[..., 2]**2)
Cr_vf = np.sqrt(vfjabr[..., 1]**2 + vfjabr[..., 2]**2)
hr_vf = np.arctan2(vfjabr[..., 2], vfjabr[..., 1])
Ct_vf = np.sqrt(vfjabt[..., 1]**2 + vfjabt[..., 2]**2)
ht_vf = np.arctan2(vfjabt[..., 2], vfjabt[..., 1])
fC = Cr_s.mean() / Cr_vfb.mean()
vfjabr[..., 1] = fC * Cr_vf * np.cos(hr_vf)
vfjabr[..., 2] = fC * Cr_vf * np.sin(hr_vf)
vfjabt[..., 1] = fC * Ct_vf * np.cos(ht_vf)
vfjabt[..., 2] = fC * Ct_vf * np.sin(ht_vf)
vfbjabt, vfbjabr, vfbDEi = gamut_slicer(
vfjabt,
vfjabr,
out='jabt,jabr,DEi',
nhbins=nhbins,
start_hue=start_hue,
normalize_gamut=normalize_gamut,
normalized_chroma_ref=normalized_chroma_ref,
close_gamut=False)
scale_factor = cri_type['scale']['cfactor']
scale_fcn = cri_type['scale']['fcn']
vfRfhi, vfRcshi, vfRhshi = jab_to_rhi(
jabt=vfbjabt,
jabr=vfbjabr,
DEi=vfbDEi,
cri_type=cri_type,
scale_factor=scale_factor,
scale_fcn=scale_fcn,
use_bin_avg_DEi=True
) # [:-1,...] removes last row from jab as this was added to close the gamut.
Rfhi_vf[:, i:i + 1] = vfRfhi
Rhshi_vf[:, i:i + 1] = vfRhshi
Rcshi_vf[:, i:i + 1] = vfRcshi
# Create dict with CRI info:
data = {'SPD' : SPD, 'cct' : cct, 'duv' : duv, 'bjabt' : bjabt, 'bjabr' : bjabr,\
'Rf' : Rf, 'Rg' : Rg, 'Rfi': Rfi, 'Rfhi' : Rfhi, 'Rchhi' : Rcshi, 'Rhshi' : Rhshi, \
'Rt' : Rt, 'Rti' : Rti, 'Rfhi_vf' : Rfhi_vf, 'Rfcshi_vf' : Rcshi_vf, 'Rfhshi_vf' : Rhshi_vf, \
'dataVF' : dataVF,'cri_type' : cri_type}
return data
def fit_ellipse(xy, center_on_mean_xy=False):
"""
Fit an ellipse to supplied data points.
Args:
:xy:
| coordinates of points to fit (Nx2 array)
:center_on_mean_xy:
| False, optional
| Center ellipse on mean of xy
| (otherwise it might be offset due to solving
| the contrained minization problem: aT*S*a, see ref below.)
Returns:
:v:
| vector with ellipse parameters [Rmax,Rmin, xc,yc, theta]
Reference:
1. Fitzgibbon, A.W., Pilu, M., and Fischer R.B.,
Direct least squares fitting of ellipsees,
Proc. of the 13th Internation Conference on Pattern Recognition,
pp 253–257, Vienna, 1996.
"""
# remove centroid:
# center = xy.mean(axis=0)
# xy = xy - center
# Fit ellipse:
x, y = xy[:, 0:1], xy[:, 1:2]
D = np.hstack((x * x, x * y, y * y, x, y, np.ones_like(x)))
S, C = np.dot(D.T, D), np.zeros([6, 6])
C[0, 2], C[2, 0], C[1, 1] = 2, 2, -1
U, s, V = np.linalg.svd(np.dot(np.linalg.inv(S), C))
e = U[:, 0]
# E, V = np.linalg.eig(np.dot(np.linalg.inv(S), C))
# n = np.argmax(np.abs(E))
# e = V[:,n]
# get ellipse axis lengths, center and orientation:
b, c, d, f, g, a = e[1] / 2, e[2], e[3] / 2, e[4] / 2, e[5], e[0]
# get ellipse center:
num = b * b - a * c
if num == 0:
xc = 0
yc = 0
else:
xc = ((c * d - b * f) / num)
yc = ((a * f - b * d) / num)
# get ellipse orientation:
theta = np.arctan2(np.array(2 * b), np.array((a - c))) / 2
# if b == 0:
# if a > c:
# theta = 0
# else:
# theta = np.pi/2
# else:
# if a > c:
# theta = np.arctan2(2*b,(a-c))/2
# else:
# theta = np.arctan2(2*b,(a-c))/2 + np.pi/2
# axis lengths:
up = 2 * (a * f * f + c * d * d + g * b * b - 2 * b * d * f - a * c * g)
down1 = (b * b - a * c) * ((c - a) * np.sqrt(1 + 4 * b * b / ((a - c) *
(a - c))) -
(c + a))
down2 = (b * b - a * c) * ((a - c) * np.sqrt(1 + 4 * b * b / ((a - c) *
(a - c))) -
(c + a))
a, b = np.sqrt((up / down1)), np.sqrt((up / down2))
# assert that a is the major axis (otherwise swap and correct angle)
if (b > a):
b, a = a, b
# ensure the angle is betwen 0 and 2*pi
theta = fmod(theta, 2.0 * np.pi)
if center_on_mean_xy == True:
xc, yc = xy.mean(axis=0)
return np.hstack((a, b, xc, yc, theta))