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This specifies that the angular distribution of the source is derived from an image, either read from file or one previously created (the latter is currently not supported). name is a string used for identification purposes. Note that the ‘file’ optional argument is for now not optional; it must be specified.
The following optional arguments are recognized:
file
The name of the image file
format
The format of the file. If not specified, B<raygen> will attempt to guess at the format. It may be one of the following:
The pixel values are in ASCII. Values are separated by whitespace
(including newlines). The file does not contain any information about
the pixel size or dimensions; you must specify these using the
pixsz
, pixsz_x
, pixsz_y
, nx
, ny
arguments.
The pixel values are stored as binary double precision floating point
numbers. The file does not contain any information about the pixel size
or dimensions; you must specify these using the pixsz
,
pixsz_x
, pixsz_y
, nx
, ny
arguments.
The pixel values are stored as binary single precision floating point
numbers. The file does not contain any information about the pixel size
or dimensions; you must specify these using the pixsz
,
pixsz_x
, pixsz_y
, nx
, ny
arguments.
The image is a standard FITS image. The pixel size may be specified by
the ‘CDELT’n FITS keywords, or by the optional
pixsz
, pixsz_x
, pixsz_y
arguments. If they are not
specified, the default is 0.5 seconds of arc. If the pixel size is
specified in the FITS file, the units for the size may be specified with
the ‘CUNIT’n FITS keywords. If not, degrees are
assumed. The FITS keywords ‘CRPIX’n and ‘CRVAL’n
are supported.
If the FITS image has a coordinate with a ‘CTYPE’ whose value
begins with ‘RA’, it is taken to be in the standard Astronomical
Right Ascension coordinate system, and the X axis flip
flag is
turned on automatically (as in that system the X pixel increment
is negative, which leads to incorrectly flipped images otherwise).
The image is in the Portable Bitmap format. The dimensions of the image
are encoded in the file. The user must specify the size of the pixels
using the optional pixsz
, pixsz_x
, pixsz_y
arguments
The image is in the Portable Grayscale Map format. The dimensions of
the image are encoded in the file. The user must specify the size of
the pixels using the optional pixsz
, pixsz_x
,
pixsz_y
arguments
nx
ny
The dimensions of the image. Depending upon the image format, this may be specified in the image file.
pixsz
pixsz_x
pixsz_y
The size of the pixels. Pixels need not be square. Depending upon the image format, this may be specified in the image file.
theta
The distance from the optical axis to the center of the rectangle, in radians. If not specified, it defaults to ‘0’.
phi
The azimuth about the optical axis, in radians. If not specified, it defaults to ‘0’.
z
The Z coordinate of the source. It defaults to an infinitely distant source.
clip
The minimum value of pixel to raytrace. Pixels with values less than this are ignored.
flip
This takes one of the following values:
x
The image is flipped along the X axis.
y
The image is flipped along the Y axis.
xy
The image is flipped along both the X and Y axes.
point_idx_x
point_idx_y
The pixel index (possibly fractional) of the position in the image which
corresponds to the angular source position specified by theta
and
phi
. You may also specify this indirectly via
point_wcs_x
/point_wcs_y
and
ref_idx_x
/ref_idx_y
and ref_wcs_x
/ref_wcs_y
.
point_wcs_x
point_wcs_y
The WCS position which corresponds to the angular source position
specified by theta
and phi
. This is used in conjunction
with ref_idx_x
/ref_idx_y
and ref_wcs_x
/ref_wcs_y
.
ref_wcs_x
ref_wcs_y
The WCS position of a reference point in the image. This is used in conjunction
with ref_idx_x
/ref_idx_y
and point_wcs_x
/point_wcs_y
.
ref_idx_x
ref_idx_y
The pixel index (possibly fractional) of the reference point in the
image. This is used in conjunction with
ref_wcs_x
/ref_wcs_y
and
point_wcs_x
/point_wcs_y
.
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