toasty tile-allsky
¶
The tile-allsky
command takes a single image representing a full sphere and
samples it into a TOAST tiling.
Usage¶
toasty tile-allsky
[standard image-loading options]
[--placeholder-thumbnail]
[--outdir DIR]
[--projection TYPE]
{IMAGE-PATH}
{TOAST-DEPTH}
See the Standard image-loading options section for documentation on those options.
The IMAGE-PATH
argument gives the filename of the input image. Its
projection onto the sphere should be specified with the --projection
option.
The TOAST-DEPTH
argument specifies the resolution level of the TOAST
pixelization that will be generated. A depth of 0 means that the image will be
sampled onto a single 256×256 tile, each pixel in the tile having an angular
size of about 0.6 deg². A depth of 1 means that the image will be sampled onto
four tiles, for a total resolution of 512×512 and an average pixel area of
0.16 deg². A depth of 8 means that there will be 65,536 tiles and 4.3 billion
pixels, with an average pixel area of about (11 arcsec)². The appropriate choice
of the depth depends on your application.
The --outdir DIR
option specifies where the output data should be written.
If unspecified, the data root will be the current directory.
The --projection TYPE
option specifies how the surface of the sphere is
mapped on to the image. Allowed types are:
plate-carree
(the default) — the image uses a “plate carrée”, AKA equirectangular or geographic, projection. The image will typically be about twice as wide as it is tall. Interpreted as a sky image, the north celestial pole is at the top of the image, RA = Dec = 0 is at the image center, and RA increases to the left.plate-carree-galactic
— like the above, but the image is in Galactic coordinates rather than (celestial) equatorial. This is often the case for all-sky astronomical press release images.plate-carree-planet
— like the above, but the image is that of a planet and so the sense of the longitude/RA axis is inverted. Longitude increases to the right. This is the format in which planetary maps are typically represented. If you use this option when you should have usedplate-carree
, or vice versa, your map come out flipped horizontally.
If the --placeholder-thumbnail
argument is given, an all-black placeholder
thumbnail will be created. Otherwise, the thumbnail will be created by
downsampling the input image. This operation can actually be the most
memory-intensive part of the process, and can yield poor results with
mostly-empty images. You can avoid this by using this argument and then invoking
toasty make-thumbnail with a better-suited input image.
Details¶
This command will create the highest-resolution tile layer, corresponding to the
DEPTH
argument, and emit an index_rel.wtml
file containing projection
information and template metadata.