HiPS generation options

This page describes in detail some of the options that can be used to control reproject_to_hips() (see Generating HiPS datasets for an introduction).

Setting the maximum order

The default behavior of reproject_to_hips() is to automatically pick a sensible maximum order/depth for the HiPS dataset based on the input data resolution, but it is also possible to set this explicitly:

>>> hdu = fits.open(get_pkg_data_filename('galactic_center/gc_2mass_k.fits'))[0]
>>> reproject_to_hips(hdu,
...                   output_directory='gc_2mass_k_level',
...                   coord_system_out='equatorial',
...                   reproject_function=reproject_interp,
...                   level=3)

Setting/overriding properties

A HiPS dataset contains a properties file which describes the HiPS dataset. Some of the parameters are set by reproject_to_hips() by default. Of these, some cannot be overridden (such as tile size and format), but others can be overridden or set if they were not present in the first place. A list of all properties can be found in the HiPS 1.0 standard.

You can set/override properties by passing a dictionary to the properties parameter:

>>> hdu = fits.open(get_pkg_data_filename('galactic_center/gc_2mass_k.fits'))[0]
>>> reproject_to_hips(hdu,
...                   output_directory='gc_2mass_k_custom_properties',
...                   coord_system_out='equatorial',
...                   reproject_function=reproject_interp,
...                   properties={'obs_title': 'My favorite dataset',
...                               'hips_pixel_cut': '400 1000',
...                               'creator_did': 'ivo://centre/P/favorite-dataset'})

Progress bar

Depending on the size of the input image and the maximum order/depth of the HiPS data to be generated, the process of reprojection can in some cases be slow due to the number of tiles to be generated. To track the progress, you can pass a callable such as a function, to the progress_bar option. This callable should take an iterable and yield each of them in time, and can draw/update the progress bar. One option is to use the tqdm package:

>>> from tqdm import tqdm
>>> hdu = fits.open(get_pkg_data_filename('galactic_center/gc_2mass_k.fits'))[0]
>>> reproject_to_hips(hdu,
...                   output_directory='gc_2mass_k_custom_progress',
...                   coord_system_out='equatorial',
...                   reproject_function=reproject_interp,
...                   progress_bar=tqdm)
100%|█████████████████████████████████████████████| 6/6 [00:00<00:00,  6.13it/s]

Multi-threading

By default, tiles are computed and written out in a single thread, but it is possible to enable multi-threading, either by setting threads=True (which automatically selects the number of threads), or e.g. threads=8 to set the number of threads explicitly.