ImageSet

class wwt_data_formats.imageset.ImageSet(**kwargs)

Bases: wwt_data_formats.LockedXmlTraits, wwt_data_formats.abcs.UrlContainer

A set of images.

Attributes Summary

band_pass	The bandpass of the image data.
base_degrees_per_tile	The angular scale of the image.
base_tile_level	The level of the highest (coarsest-resolution) tiling available.
bottoms_up	TBD.
center_x	The horizontal location of the center of the image’s projection coordinate system.
center_y	The vertical location of the center of the image’s projection coordinate system.
credits	Textual credits for the image originator.
credits_url	A URL giving the source of the image or more information about its creation.
data_set_type	The renderer mode to which these data apply.
dem_url	The URL of the DEM data.
description	A textual description of the imagery.
elevation_model	TBD.
file_type	The extension of the image file(s) in this set, including a leading period.
generic	TBD.
mean_radius	TBD.
msr_community_id	The ID number of the WWT Community that this content came from.
msr_component_id	The ID number of this content item on the WWT Communities system.
name	A name used to refer to this imageset.
offset_x	The horizontal positioning of the image relative to its projection coordinate system.
offset_y	The vertical positioning of the image relative to its projection coordinate system.
permission	TBD.
projection	The type of projection used to place this image on the sky.
quad_tree_map	TBD.
reference_frame	TBD.
rotation_deg	The rotation of image’s projection coordinate system, in degrees.
sparse	TBD.
stock_set	TBD.
thumbnail_url	A URL to a standard WWT thumbnail representation of this imageset.
tile_levels	The number of levels of tiling.
url	The URL of the image data.
width_factor	This is a legacy parameter.

Methods Summary

set_position_from_wcs(headers, width, height)	Set the positional information associated with this imageset to match a set of WCS headers.
wcs_headers_from_position()	Compute a set of WCS headers for this ImageSet’s positional information.

Attributes Documentation

band_pass

The bandpass of the image data.

base_degrees_per_tile

The angular scale of the image.

For untiled images, should be the pixel scale: the number of degrees per pixel in the vertical direction. Non-square pixels are not supported.

For tiled images, this is the height of the image with its dimensions padded out to the next largest power of 2 for tiling purposes. If a square image is 1200 pixels tall and has a height of 0.016 deg, the padded height would be 2048 pixels and this parameter should be set to 0.016 * 2048 / 1200 = 0.0273.

base_tile_level

The level of the highest (coarsest-resolution) tiling available.

This should be zero except for special circumstances.

bottoms_up

TBD.

center_x

The horizontal location of the center of the image’s projection coordinate system.

For sky images, this is a right ascension in degrees.

center_y

The vertical location of the center of the image’s projection coordinate system.

For sky images, this is a declination in degrees.

credits

Textual credits for the image originator.

credits_url

A URL giving the source of the image or more information about its creation.

data_set_type

The renderer mode to which these data apply.

Possible values are "Earth", "Planet", "Sky", "Panorama", "SolarSystem", and "Sandbox".

dem_url

The URL of the DEM data.

Either a URL or a URL template. TODO: details

description

A textual description of the imagery.

elevation_model

TBD.

file_type

The extension of the image file(s) in this set, including a leading period.

generic

TBD.

mean_radius

TBD.

msr_community_id

The ID number of the WWT Community that this content came from.

msr_component_id

The ID number of this content item on the WWT Communities system.

name

A name used to refer to this imageset.

Various parts of the WWT internals reference imagesets by this name, so it should be distinctive.

offset_x

The horizontal positioning of the image relative to its projection coordinate system.

For untiled sky images, the image is by default positioned such that its lower left lands at the center of the projection coordinate system (namely, center_x and center_y). The offset is measured in pixels and moves the image leftwards. Therefore, offset_x = image_width / 2 places the center of the image at center_x. This parameter is therefore analogous to the WCS keyword CRVAL1.

For tiled sky images, the offset is measured in degrees, and a value of zero means that the center of the image lands at the center of the projection coordinate system.

offset_y

The vertical positioning of the image relative to its projection coordinate system.

For untiled sky images, the image is by default positioned such that its lower left lands at the center of the projection coordinate system (namely, center_x and center_y). The offset is measured in pixels and moves the image downwards. Therefore, offset_y = image_height / 2 places the center of the image at center_y. This parameter is therefore analogous to the WCS keyword CRVAL2.

For tiled sky images, the offset is measured in degrees, and a value of zero means that the center of the image lands at the center of the projection coordinate system.

permission

TBD.

projection

The type of projection used to place this image on the sky.

For untiled images, this should be “SkyImage”. For tiled images, it should be “Tan”. The set_position_from_wcs() method will set this value appropriately based on tile_levels.

quad_tree_map

TBD.

reference_frame

TBD.

rotation_deg

The rotation of image’s projection coordinate system, in degrees.

For sky images, this is East from North, i.e. counterclockwise.

sparse

TBD.

stock_set

TBD.

thumbnail_url

A URL to a standard WWT thumbnail representation of this imageset.

tile_levels

The number of levels of tiling.

Should be zero for untiled images. An image with tile_levels = 1 has been broken into four tiles, each 256x256 pixels. For tile_levels = 2, there are sixteen tiles, and the padded height of the tiled area is 256 * 2**2 = 1024 pixels. Image with dimensions of 2048 pixels or smaller do not need to be tiled, so if this parameter is nonzero it will usually be 4 or larger.

url

The URL of the image data.

Either a URL or a URL template. TODO: details

width_factor

This is a legacy parameter. Leave it at 2.

Methods Documentation

set_position_from_wcs(headers, width, height, place=None, fov_factor=1.7)

Set the positional information associated with this imageset to match a set of WCS headers.

Parameters

headersHeader or string-keyed dict-like

A set of FITS-like headers including WCS keywords such as CRVAL1.

widthpositive integer

The width of the image associated with the WCS, in pixels.

heightpositive integer

The height of the image associated with the WCS, in pixels.

placeoptional Place

If specified, the centering and zoom level of the Place object will be set to match the center and size of this image.

fov_factoroptional float

If place is provided, its zoom level will be set so that the angular height of the client viewport is this factor times the angular height of the image. The default is 1.7.

Returns

self

For convenience in chaining function calls.

Notes

Certain of the ImageSet parameters take on different meanings depending on whether the image in question is a tiled “study” or not. This method will alter its behavior depending on whether the tile_levels attribute is greater than zero. If you are computing coordinates for a tiled study, make sure to set this parameter before calling this function.

For the time being, the WCS must be equatorial using the gnomonic (TAN) projection.

Required keywords in headers are:

• CTYPE1 and CTYPE2

• CRVAL1 and CRVAL2

• CRPIX1 and CRPIX2

• Either: - CDELT1, CDELT2, PC1_1, and PC1_2; or - CD1_1, CD2_2

If present PC1_2, PC2_1, CD1_2, and/or CD2_1 are used. If absent, they are assumed to be zero.

wcs_headers_from_position()

Compute a set of WCS headers for this ImageSet’s positional information.

Returns

A string-keyed dict-like containing FITS/WCS header keywords such as

CTYPE1, CRPIX1, etc.

Notes

At the moment, this function only works for ImageSets with a projection type of SKY_IMAGE. Support for other projections might be added later, if the need arises..