Sip¶
- class astropy.wcs.Sip(*a, b, ap, bp, crpix*)¶
Bases:
object
The
Sip
class performs polynomial distortion correction using the SIP convention in both directions.- Parameters:
- a
ndarray
The
A_i_j
polynomial for pixel to focal plane transformation asdouble array[m+1][m+1]
. Its size must be (m + 1, m + 1) where m =A_ORDER
.- b
ndarray
The
B_i_j
polynomial for pixel to focal plane transformation asdouble array[m+1][m+1]
. Its size must be (m + 1, m + 1) where m =B_ORDER
.- ap
ndarray
The
AP_i_j
polynomial for pixel to focal plane transformation asdouble array[m+1][m+1]
. Its size must be (m + 1, m + 1) where m =AP_ORDER
.- bp
ndarray
The
BP_i_j
polynomial for pixel to focal plane transformation asdouble array[m+1][m+1]
. Its size must be (m + 1, m + 1) where m =BP_ORDER
.- crpix
ndarray
The reference pixel as
double array[2]
.
- a
Notes
Shupe, D. L., M. Moshir, J. Li, D. Makovoz and R. Narron. 2005. “The SIP Convention for Representing Distortion in FITS Image Headers.” ADASS XIV.
Attributes Summary
double array[a_order+1][a_order+1]
Focal plane transformation matrix.int
(read-only) Order of the polynomial (A_ORDER
).double array[ap_order+1][ap_order+1]
Focal plane to pixel transformation matrix.int
(read-only) Order of the polynomial (AP_ORDER
).double array[b_order+1][b_order+1]
Pixel to focal plane transformation matrix.int
(read-only) Order of the polynomial (B_ORDER
).double array[bp_order+1][bp_order+1]
Focal plane to pixel transformation matrix.int
(read-only) Order of the polynomial (BP_ORDER
).double array[naxis]
Coordinate reference pixels (CRPIXja
) for each pixel axis.Methods Summary
sip_foc2pix(foccrd, origin) ->
double array[ncoord][nelem]
sip_pix2foc(pixcrd, origin) ->
double array[ncoord][nelem]
Attributes Documentation
- a¶
double array[a_order+1][a_order+1]
Focal plane transformation matrix.The SIP
A_i_j
matrix used for pixel to focal plane transformation.Its values may be changed in place, but it may not be resized, without creating a new
Sip
object.
- a_order¶
int
(read-only) Order of the polynomial (A_ORDER
).
- ap¶
double array[ap_order+1][ap_order+1]
Focal plane to pixel transformation matrix.The SIP
AP_i_j
matrix used for focal plane to pixel transformation. Its values may be changed in place, but it may not be resized, without creating a newSip
object.
- ap_order¶
int
(read-only) Order of the polynomial (AP_ORDER
).
- b¶
double array[b_order+1][b_order+1]
Pixel to focal plane transformation matrix.The SIP
B_i_j
matrix used for pixel to focal plane transformation. Its values may be changed in place, but it may not be resized, without creating a newSip
object.
- b_order¶
int
(read-only) Order of the polynomial (B_ORDER
).
- bp¶
double array[bp_order+1][bp_order+1]
Focal plane to pixel transformation matrix.The SIP
BP_i_j
matrix used for focal plane to pixel transformation. Its values may be changed in place, but it may not be resized, without creating a newSip
object.
- bp_order¶
int
(read-only) Order of the polynomial (BP_ORDER
).
- crpix¶
double array[naxis]
Coordinate reference pixels (CRPIXja
) for each pixel axis.
Methods Documentation
- foc2pix()¶
sip_foc2pix(foccrd, origin) ->
double array[ncoord][nelem]
Convert focal plane coordinates to pixel coordinates using the SIP polynomial distortion convention.
- Parameters:
- foccrd
ndarray
Array of focal plane coordinates as
double array[ncoord][nelem]
.- origin
python:int
Specifies the origin of pixel values. The Fortran and FITS standards use an origin of 1. Numpy and C use array indexing with origin at 0.
- foccrd
- Returns:
- pixcrd
ndarray
Returns an array of pixel coordinates as
double array[ncoord][nelem]
.
- pixcrd
- Raises:
MemoryError
Memory allocation failed.
ValueError
Invalid coordinate transformation parameters.
- pix2foc()¶
sip_pix2foc(pixcrd, origin) ->
double array[ncoord][nelem]
Convert pixel coordinates to focal plane coordinates using the SIP polynomial distortion convention.
- Parameters:
- pixcrd
ndarray
Array of pixel coordinates as
double array[ncoord][nelem]
.- origin
python:int
Specifies the origin of pixel values. The Fortran and FITS standards use an origin of 1. Numpy and C use array indexing with origin at 0.
- pixcrd
- Returns:
- foccrd
ndarray
Returns an array of focal plane coordinates as
double array[ncoord][nelem]
.
- foccrd
- Raises:
MemoryError
Memory allocation failed.
ValueError
Invalid coordinate transformation parameters.