def fareyMapping(N):
'''
Print out the Farey/rational angle mapping to the finite angle set.
The angles are based on L1 norm minimal rational angle set.
Also returns the finite angle set, matching rational angles and No. of bins lists
'''
#create angle set with Farey vectors
fareyVectors = farey.Farey()
fareyVectors.compactOn()
fareyVectors.generateFiniteWithCoverage(N)
# angles = fareyVectors.vectors
# print "Number of Projections:", len(angles)
# print fareyVectors.finiteAngles
# print fareyVectors.vectors
#sort to reorder result for prettier printing
finiteAnglesSorted, anglesSorted = fareyVectors.sort('finite')
#print mapping
BList = []
for finiteAngle, angle in zip(finiteAnglesSorted, anglesSorted):
p, q = farey.get_pq(angle)
B = farey.projectionLength(angle, N, N)
BList.append(B)
print("m:", finiteAngle, "p:", p, "q:", q, "B:", B)
return finiteAnglesSorted, anglesSorted, BList
def getMojetteSlice(angle, P, Q, data, center=False):
'''
Get the Mojette slice (at angle) of a NxN discrete array using the discrete non-periodic Fourier slice theorem.
This can be applied to the DFT or the NTT arrays.
'''
N, N = data.shape
p, q = farey.get_pq(angle)
B = getMojetteProjectionLength(angle, P, Q)
# print "B Mojette:", B
offset = 0.0
if center:
offset = N/2.0
slice = np.zeros(2*B-1, dtype=data.dtype)
# slice = np.zeros(B, dtype=data.dtype)
for translate in range(0, B):
translateP = (p*translate)%N #has issues in C, may need checking
translatePConjugate = (N-translateP+offset)%N #has issues in C, may need checking
translateQ = (q*translate)%N #has issues in C, may need checking
translateQConjugate = (N-translateQ+offset)%N #has issues in C, may need checking
slice[translate] = data[(translateQ+offset)%N, (translateP+offset)%N]
if translate != 0:
slice[(2*B-1-translate)%N] = data[translateQConjugate, translatePConjugate]
# slice[(B-translate)%N] = data[translateQConjugate, translatePConjugate]
return slice
def computeKatzLines(kSpace, anglesSorted, finiteAnglesSorted, K, centered = True, twoQuads = False):
'''
compute finite lines coordinates given Katz criterion
Returns a list or list of slice 2-tuples and corresponding list of angles and m values
perp computes the perpendicular (s) lines as well
'''
N, M = kSpace.shape
lines = []
angles = []
mValues = []
for m, angle in zip(finiteAnglesSorted, anglesSorted):
if isKatzCriterion(N, N, angles, K):
print("Katz Criterion Met. Breaking")
break
m, inv = farey.toFinite(angle, N)
u, v = radon.getSliceCoordinates2(m, kSpace, centered)
lines.append((u,v))
mValues.append(m)
angles.append(angle)
#second quadrant
if twoQuads:
if m != 0 and m != N: #dont repeat these
m = N-m
u, v = radon.getSliceCoordinates2(m, kSpace, centered)
lines.append((u,v))
mValues.append(m)
p, q = farey.get_pq(angle)
newAngle = farey.farey(-p,q) #not confirmed
angles.append(newAngle)
return lines, angles, mValues
def mojetteProjection(projection, N, angle, P, Q):
'''
Convert a finite projection into a Mojette projection for given (p,q).
Assumes you have correctly determined (p,q) for the m value of the finite projection.
'''
# dyadic = True
# if N % 2 == 1: # if odd, assume prime
# dyadic = False
p, q = farey.get_pq(angle)
B = farey.projectionLength(angle, P, Q) #no. of bins
m, inv = farey.toFinite(angle, N)
translateOffset, perp = farey.finiteTranslateOffset(angle, N, P, Q)
mojetteProj = np.zeros(B)
angleSign = p * q
'''if nt.is_coprime(q, N):
inv = q
else: #perp projection
inv = p
for translate, bin in enumerate(projection):
translateMojette = int((inv*translate)%N)
if angleSign >= 0 and perp: #Reverse for perp
translateMojette = int(translateOffset) - translateMojette
else:
translateMojette += int(translateOffset)
print "TR:", translate, "Tm:", translateMojette
mojetteProj[translateMojette] += bin'''
for translate, bin in enumerate(mojetteProj):
if angleSign >= 0 and perp: #Reverse for perp
translateMojette = int(translateOffset) - int(translate)
else:
translateMojette = int(translate) - int(translateOffset)
if translateMojette < 0:
translateFinite = (N - (inv * abs(translateMojette)) % N) % N
else:
translateFinite = (inv * translateMojette
) % N #has issues in C, may need checking
mojetteProj[translate] += projection[translateFinite]
# print "TR:", translateFinite, "TM:", translate
return mojetteProj
def isKatzCriterion(P, Q, angles, K=1):
'''
Return true if angle set meets Katz criterion for exact reconstruction of
discrete arrays
'''
sumOfP = 0
sumOfQ = 0
n = len(angles)
for j in range(0, n):
p, q = farey.get_pq(angles[j])
sumOfP += abs(p)
sumOfQ += abs(q)
if sumOfP > K * P or sumOfQ > K * Q:
return True
else:
return False
