astrohack.image_comparison_tool

Functions

compare_fits_images(image, reference_image, ...[, ...])

Compares a set of images to a set of reference images.

rms_table_from_zarr_datatree(zarr_data_tree, table_file)

Goes through the data in a zarr DataTree created by compare_fits_images.

Module Contents

compare_fits_images(image: str | List[str], reference_image: str | List[str], telescope_name: str, destination: str, comparison: str = 'direct', zarr_container_name: str | None = None, plot_resampled: bool = False, plot_percentuals: bool = False, plot_reference: bool = False, plot_original: bool = False, plot_divided_image: bool = False, plot_scatter: bool = True, z_scale_limits: List[float] | Tuple | numpy.ndarray | None = None, colormap: str = 'viridis', dpi: int = 300, display: bool = False, export_to_fits: bool = False, parallel: bool = False)[source]

Compares a set of images to a set of reference images.

Parameters:

  • image (list or str) – FITS image or list of FITS images to be compared.

  • reference_image (list or str) – FITS image or list of FITS images that serve as references.

  • telescope_name (str) – Name of the telescope used. Used for masking.

  • destination (str) – Name of directory onto which save plots

  • comparison (str, optional) – Type of comparison to be made between images, “direct” or “scaled”, default is “direct”.

  • zarr_container_name (str, optional) – Name of the Zarr container to contain the created datatree, default is None, i.e. DataTree is not saved to disk.

  • plot_resampled (bool, optional) – Plot the resampled data array used in the comparison, default is False.

  • plot_reference (bool, optional) – Plot the reference image used in the comparison, default is False.

  • plot_original (bool, optional) – Plot the unresampled image used as input, default is False.

  • plot_percentuals (bool, optional) – Plot the residuals in percent of reference image as well, default is False.

  • plot_divided_image (bool, optional) – Plot the divided image between Image and its reference, default is False.

  • plot_scatter (bool, optional) – Make a scatter plot of the Image against its reference image, default is True.

  • z_scale_limits (list, np.array, tuple, optional) – Z scale for original, resampled, reference and residual images in the image units, default is None (get z scale limits from data)

  • colormap (str, optional) – Colormap to be used on image plots, default is “viridis”.

  • dpi (int, optional) – dots per inch to be used in plots, default is 300.

  • display (bool, optional) – Display plots inline or suppress, defaults to True

  • export_to_fits (bool, optional) – Export created images to FITS files inside destination, default is False.

  • parallel (bool, optional) – If True will use an existing astrohack client to do comparison in parallel, default is False

Returns:

DataTree object containing all the comparisons executed

Return type:

xr.DataTree

Compares pairs of FITS images pixel by pixel using a mask based on telescope parameters to exclude problematic regions such as shadows caused by the secondary mirror or the arms supporting it. By default, 2 products are produced, a plot of the residuals image, i.e. (Reference - Image) and a scatter plot of the Reference against the Image. If necessary a resample of Image is conducted to allow for pixel by pixel comparison.

Comparison:

Two types of comparison between the images are available:

  • direct: Where the residuals are simply computed as Reference - Image.

  • scaled: Where the residuals are Reference - Factor * Image, with Factor = median(Reference/Image).

Plots:

A plot of the residuals of the comparison is always produced. However, a few extra plots can be produced and their production is controlled by the plot_ parameters, these are:

  • plot_resampled: Activates plotting of the resampled data used in the comparison, default is False as this is just the data on the FITS file resampled to the reference sampling.

  • plot_percentuals: Activates the plotting of the residuals as a perdentage of the Reference Image, default is False as this is just another view on the residuals.

  • plot_reference: Activates the plotting of the reference image used in the comparison, default is False as this is just the data on the reference FITS file.

  • plot_original: Activates the plotting of the unresampled data, default is False as this is just the data on the FITS file

  • plot_divided_image: Activates the plotting of Reference/Image, default is False. This plot is only available when using “scaled” comparison.

  • plot_scatter: Activates the creation of a scatter plot of Reference vs Image, with a linear regression, default is True.

Storage on disk:

By default, this function only produces plots, but this can be changed using two parameters:

  • zarr_container_name: If this parameter is not None a Zarr container will be created on disk with the contents of the produced DataTree.

  • export_to_fits: If set to True will produce FITS files of the produced images and store them at destination.

Return type:

This funtion returns a Xarray DataTree containing the Xarray DataSets that represent Image and Reference. The nodes in this DataTree are labelled according to the filenames given as input for easier navigation.

rms_table_from_zarr_datatree(zarr_data_tree: str, table_file: str, rms_unit: str = 'mm', print_table: bool = False)[source]

Goes through the data in a zarr DataTree created by compare_fits_images.

Parameters:

  • zarr_data_tree (str) – Name on disk of the Zarr container holding a compare_fits_image DataTree.

  • table_file (str) – Name of the ASCII file to be created on disk to contain the RMS table

  • rms_unit (str, optional) – Unit for the RMSes in the table, default is ‘mm’.

  • print_table (bool, optional) – Print table on terminal, default is False.

Returns:

None

Return type:

NoneType