Step Arguments

The resample step has the following optional arguments that control the behavior of the processing and the characteristics of the resampled image.

--pixfrac (float, default=1.0)

The fraction by which input pixels are “shrunk” before being drizzled onto the output image grid, given as a real number between 0 and 1.

--kernel (str, default=’square’)

The form of the kernel function used to distribute flux onto the output image. Available kernels are square, gaussian, point, tophat, turbo, lanczos2, and lanczos3.

--pixel_scale_ratio (float, default=1.0)

Ratio of input to output pixel scale. A value of 0.5 means the output image would have 4 pixels sampling each input pixel. Ignored when pscale are provided.

--pixel_scale (float, default=None)

Absolute pixel scale in arcsec. When provided, overrides pixel_scale_ratio.

--rotation (float, default=None)

Position angle of output image’s Y-axis relative to North. A value of 0.0 would orient the final output image to be North up. The default of None specifies that the images will not be rotated, but will instead be resampled in the default orientation for the camera with the x and y axes of the resampled image corresponding approximately to the detector axes. Ignored when transform is provided.

--output_shape (tuple of int, default=None)

Shape of the image (data array) using “standard” nx first and ny second (as opposite to the numpy.ndarray convention - ny first and nx second). This value will be assigned to pixel_shape and array_shape properties of the returned WCS object. When supplied from command line, it should be a comma-separated list of integers nx, ny.

--crpix (tuple of float, default=None)

Position of the reference pixel in the image array in the x, y order. If crpix is not specified, it will be set to the center of the bounding box of the returned WCS object. When supplied from command line, it should be a comma-separated list of floats.

--crval (tuple of float, default=None)

Right ascension and declination of the reference pixel. Automatically computed if not provided. When supplied from command line, it should be a comma-separated list of floats.

--fillval (str, default=’INDEF’)

The value to assign to output pixels that have zero weight or do not receive any flux from any input pixels during drizzling.

--weight_type (str, default=’ivm’)

The weighting type for each input image. If weight_type=ivm (the default), the scaling value will be determined per-pixel using the inverse of the read noise (VAR_RNOISE) array stored in each input image. If the VAR_RNOISE array does not exist, the variance is set to 1 for all pixels (equal weighting). If weight_type=exptime, the scaling value will be set equal to the exposure time found in the image header.

--single (bool, default=False)

If set to True, resample each input image into a separate output. If False (the default), each input is resampled additively (with weights) to a common output

--blendheaders (bool, default=True)

Blend metadata from all input images into the resampled output image.

--allowed_memory (float, default=None)

Specifies the fractional amount of free memory to allow when creating the resampled image. If None, the environment variable DMODEL_ALLOWED_MEMORY is used. If not defined, no check is made. If the resampled image would be larger than specified, an OutputTooLargeError exception will be generated.

For example, if set to 0.5, only resampled images that use less than half the available memory can be created.