dodrizzle

drizzle.dodrizzle.dodrizzle(insci, input_wcs, inwht, output_wcs, outsci, outwht, outcon, expin, in_units, wt_scl, wcslin_pscale=1.0, uniqid=1, xmin=0, xmax=0, ymin=0, ymax=0, pixfrac=1.0, kernel=u'square', fillval=u'INDEF', stepsize=10, wcsmap=None)

Low level routine for performing ‘drizzle’ operation.on one image.

The interface is compatible with STScI code. All images are Python ndarrays, instead of filenames. File handling (input and output) is performed by the calling routine.

Parameters:

insci : 2d array

A 2d numpy array containing the input image to be drizzled. it is an error to not supply an image.

input_wcs : 2d array

The world coordinate system of the input image.

inwht : 2d array

A 2d numpy array containing the pixel by pixel weighting. Must have the same dimensions as insci. If none is supplied, the weghting is set to one.

output_wcs : wcs

The world coordinate system of the output image.

outsci : 2d array

A 2d numpy array containing the output image produced by drizzling. On the first call it should be set to zero. Subsequent calls it will hold the intermediate results

outwht : 2d array

A 2d numpy array containing the output counts. On the first call it should be set to zero. On subsequent calls it will hold the intermediate results.

outcon : 2d array

A 3d numpy array holding a bitmap of which image was an input for each output pixel. Should be integer zero on first call. Subsequent calls hold intermediate results.

expin : float

The exposure time of the input image, a positive number. The exposure time is used to scale the image if the units are counts.

in_units : str

The units of the input image. The units can either be “counts” or “cps” (counts per second.)

wt_scl : float

A scaling factor applied to the pixel by pixel weighting.

wcslin_pscale : float, optional

The pixel scale of the input image. Conceptually, this is the linear dimension of a side of a pixel in the input image, but it is not limited to this and can be set to change how the drizzling algorithm operates.

uniqid : int, optional

The id number of the input image. Should be one the first time this function is called and incremented by one on each subsequent call.

xmin : float, optional

This and the following three parameters set a bounding rectangle on the input image. Only pixels on the input image inside this rectangle will have their flux added to the output image. Xmin sets the minimum value of the x dimension. The x dimension is the dimension that varies quickest on the image. If the value is zero, no minimum will be set in the x dimension. All four parameters are zero based, counting starts at zero.

xmax : float, optional

Sets the maximum value of the x dimension on the bounding box of the input image. If the value is zero, no maximum will be set in the x dimension, the full x dimension of the output image is the bounding box.

ymin : float, optional

Sets the minimum value in the y dimension on the bounding box. The y dimension varies less rapidly than the x and represents the line index on the input image. If the value is zero, no minimum will be set in the y dimension.

ymax : float, optional

Sets the maximum value in the y dimension. If the value is zero, no maximum will be set in the y dimension, the full x dimension of the output image is the bounding box.

pixfrac : float, optional

The fraction of a pixel that the pixel flux is confined to. The default value of 1 has the pixel flux evenly spread across the image. A value of 0.5 confines it to half a pixel in the linear dimension, so the flux is confined to a quarter of the pixel area when the square kernel is used.

kernel: str, optional

The name of the kernel used to combine the input. The choice of kernel controls the distribution of flux over the kernel. The kernel names are: “square”, “gaussian”, “point”, “tophat”, “turbo”, “lanczos2”, and “lanczos3”. The square kernel is the default.

fillval: str, optional

The value a pixel is set to in the output if the input image does not overlap it. The default value of INDEF does not set a value.

Returns:

A tuple with three values: a version string, the number of pixels

on the input image that do not overlap the output image, and the

number of complete lines on the input image that do not overlap the

output input image.

Other Parameters:  

stepsize

Was used when input to output mapping was computed inside the cdrizzle code. Is no longer used and only here for backwards compatibility. It may be re-used in the future if we need to use a subsampled pixel map to improve speed.

wcsmap

Was used when input to output mapping was computed inside the cdrizzle code. Is no longer used and only here for backwards compatibility.