Projects image from one WCS to another
reproject_image_grid infile outfile xsize ysize xcenter ycenter theta
pixelsize projection [resolution] [method] [coord_sys] [lookupTab]
[clobber] [verbose]
`reproject_image_grid' maps an image in one WCS reference frame to
another. For each output pixel in the matchfile it maps an
n-point polygon
onto the input image via the WCS transforms. The area of each
pixel covered in the input image is then used to compute the
output pixel value.
`reproject_image_grid' can be used to project an image w/ one tanget
point to another tanget point as is useful when merging multiple
observations or when matching data across missions.
Any Null/NaN valued pixels or pixels outside the data-subspace or
pixels outside the input image are assigned a value = 0.
reproject_image_grid infile=img.fits matchfile="none" outfile=new.fits
xcenter='12:32:54.334" ycenter="+54:45:23.996" xsize=512 ysize=512
pixelsize=0.5\" theta=0 projection=tan resolution=1 coord_sys=world
clob+
When the matchfile is set to "none"; users can create a new image
using the xcenter, ycenter, xsize, ysize, pixelsize, theta, and
projection parameters. In this example the infile image is
reprojected to a tangent point specified by the xcenter and ycenter
values.
Note: the \ before the " is to escape the " (for arc-second) from getting
interprested by the user shell (eg (ba)sh, (t)csh). If prompted for
the value the \ should not be included.
The output file name
Contains the reprojected image.
Parameter=xsize (integer required default=1 min=1 units=pixels)
Image size in X direction
Parameter=ysize (integer required default=1 min=1 units=pixels)
Image size in Y direction
X-Center of image in world coordinates
The center of the image. This is where the tangent point is located
and will be placed at the center of the image (eg at xsize/2).
This may be entered either in degrees, 210.4568777, or in
sexagesimal format, 14:59:32.998 (values not intended to be equal).
X-Center of image in world coordinates
The center of the image. This is where the tangent point is located
and will be placed at the center of the image (eg at ysize/2).
This may be entered either in degrees, 32.998666, or in
sexagesimal format, +32:59:32.312 (values not intended to be equal).
Parameter=theta (real required default=0 min=0 max=360 units=degrees)
Rotation angle (degrees)
Position angle: angle between North and +Y-axis measured counter-clockwise.
Pixel size
The size of the pixels on the sky. (Note: same value used for X and Y axes).
This value can be entered either in degrees: 1.345e-4 or
0.0001345, arc-minutes: 0.00134', or in arc-seconds: 0.495"
Type of world coordinate system
Currently only tangent plane projections are supported.
Controls quality of projection; number of points per side of polygon
An n-sided polygon that outlines the output pixel is mapped to input
image via the WCS transforms. The number of points along each side
of the pixel is the resolution parameter. A value of '1' indicated
that just the corners of the pixel will be used. A value of '2'
indicates that the corner and the middle of the pixel-edge line
segments will be use. And so on. The more points on the polygon,
the better the polygon will approximate the possibly non-linear
transform between the images. However, the more points on the
polygon, the longer the run-time of the tool.
A value of '0' can also be used. This is a special quick mode that
simply maps the center output pixel to a single input pixel and uses
that value in the output image. This can be done very quickly;
however, when something other than a simple shift of the images is
need this can result in image artifacts (for example aliasing or
'dead' regions). Also the 'method' is not applicable in this
useage. The output image is essentially "interpolated", so if the
pixel scales are different the flux will not be preserved.
Controls output normalization
The output image can either represent a conservation of "sum" (
integral over an apperature on the input and output image would give
same value) or it can represent an "average" where the
output pixel value represents an average input value.
Typically users will use "sum" to reproject the COUNTS image and
will use "average" to reproject the EXPOSURE image when making
fluxed images.
Coordinate system to do the pixel mapping in
Currently only "world" coordinate system is supported.
Logical pixels in the output image are mapped to physical pixels
which are then mapped to world coordinate (RA,Dec). These are then
mapped back to physical pixels in the input image and then back to
image pixels in the input image. [TBD: implement "physical" and
"image" coord sys's]
The header merging table
Rules to merge the headers when more than one file supplied. If
set to NONE or a blank string then the header from the first file is used.
Remove output if it exists?
Used to specify whether or not to clobber existing file that
has the same name as the specified output file
The tool chatter level
Verbose can be from 0 to 5, generating different amounts
of debugging output.
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