def PixelsToQ(data, correct_solid_angle=True):
"""
generate a q_map for sansdata. Each pixel will have 4 values: (qx,qy,q,theta)
**Inputs**
data (sans2d): data in
correct_solid_angle {Correct solid angle} (bool): Apply correction for mapping
curved Ewald sphere to flat detector
**Returns**
output (sans2d): converted to I vs. Qx, Qy
2016-04-06 Brian Maranville
"""
L2=data.metadata['det.dis']
x0=data.metadata['det.beamx'] #should be close to 64
y0=data.metadata['det.beamy'] #should be close to 64
wavelength=data.metadata['resolution.lmda']
shape=data.data.x.shape
qx=np.empty(shape,'Float64')
qy=np.empty(shape,'Float64')
x,y = np.indices(shape)
X=data.metadata['det.pixelsizex']/10.0*(x-x0) # in mm in nexus
Y=data.metadata['det.pixelsizey']/10.0*(y-y0)
r=np.sqrt(X**2+Y**2)
theta=np.arctan2(r,L2*100)/2 #remember to convert L2 to cm from meters
q=(4*np.pi/wavelength)*np.sin(theta)
alpha=np.arctan2(Y,X)
qx=q*np.cos(alpha)
qy=q*np.sin(alpha)
if correct_solid_angle:
data.data.x = data.data.x * (np.cos(theta)**3)
res=SansData()
res.data=copy(data.data)
res.metadata=deepcopy(data.metadata)
#Adding res.q
res.q = q
res.qx=qx
res.qy=qy
res.theta=theta
return res
