Next: Polygons, Previous: Tessellation library, Up: Gnuastro library [Contents][Index]

Functions related to reporting the bounding box of certain inputs are
declared in `gnuastro/box.h`. All coordinates in this header are in
the FITS format (first axis is the horizontal and the second axis is
vertical).

- Function:

*void*

**gal_box_bound_ellipse_extent***(double*`a`

, double`b`

, double`theta_deg`

, double`*extent`

) Return the maximum extent along each dimension of the given ellipse from the center of the ellipse. Therefore this is half the extent of the box in each dimension.

`a`

is the ellipse semi-major axis,`b`

is the semi-minor axis,`theta_deg`

is the position angle in degrees. The extent in each dimension is in floating point format and stored in`extent`

which must already be allocated before this function.

- Function:

*void*

**gal_box_bound_ellipse***(double*`a`

, double`b`

, double`theta_deg`

, long`*width`

) Any ellipse can be enclosed into a rectangular box. This function will write the height and width of that box where

`width`

points to. It assumes the center of the ellipse is located within the central pixel of the box.`a`

is the ellipse semi-major axis length,`b`

is the semi-minor axis,`theta_deg`

is the position angle in degrees. The`width`

array will contain the output size in long integer type.`width[0]`

, and`width[1]`

are the number of pixels along the first and second FITS axis. Since the ellipse center is assumed to be in the center of the box, all the values in`width`

will be an odd integer.

- Function:

*void*

**gal_box_bound_ellipsoid_extent***(double*`*semiaxes`

, double`*euler_deg`

, double`*extent`

) Return the maximum extent along each dimension of the given ellipsoid from its center. Therefore this is half the extent of the box in each dimension. The semi-axis lengths of the ellipsoid must be present in the 3 element

`semiaxis`

array. The`euler_deg`

array contains the three ellipsoid Euler angles in degrees. For a description of the Euler angles, see description of`gal_box_bound_ellipsoid`

below. The extent in each dimension is in floating point format and stored in`extent`

which must already be allocated before this function.

- Function:

*void*

**gal_box_bound_ellipsoid***(double*`*semiaxes`

, double`*euler_deg`

, long`*width`

) Any ellipsoid can be enclosed into a rectangular volume/box. The purpose of this function is to give the integer size/width of that box. The semi-axes lengths of the ellipse must be in the

`semiaxes`

array (with three elements). The major axis length must be the first element of`semiaxes`

. The only other condition is that the next two semi-axes must both be smaller than the first. The orientation of the major axis is defined through three proper Euler angles (ZXZ order in degrees) that are given in the`euler_deg`

array. The`width`

array will contain the output size in long integer type (in FITS axis order). Since the ellipsoid center is assumed to be in the center of the box, all the values in`width`

will be an odd integer.The proper Euler angles can be defined in many ways (which axes to rotate about). For a full description of the Euler angles, please see Wikipedia. Here we adopt the ZXZ (or \(Z_1X_2Z_3\)) proper Euler angles were the first rotation is done around the Z axis, the second one about the (rotated) X axis and the third about the (rotated) Z axis.

- Function:

*void*

**gal_box_border_from_center***(double*`center`

, size_t`ndim`

, long`*width`

, long`*fpixel`

, long`*lpixel`

) Given the center coordinates in

`center`

and the`width`

(along each dimension) of a box, return the coordinates of the first (`fpixel`

) and last (`lpixel`

) pixels. All arrays must have`ndim`

elements (one for each dimension).

- Function:

*int*

**gal_box_overlap***(long*`*naxes`

, long`*fpixel_i`

, long`*lpixel_i`

, long`*fpixel_o`

, long`*lpixel_o`

, size_t`ndim`

) An

`ndim`

-dimensional dataset of size`naxes`

(along each dimension, in FITS order) and a box with first and last (inclusive) coordinate of`fpixel_i`

and`lpixel_i`

is given. This box doesn’t necessarily have to lie within the dataset, it can be outside of it, or only partially overlap. This function will change the values of`fpixel_i`

and`lpixel_i`

to exactly cover the overlap in the input dataset’s coordinates.This function will return 1 if there is an overlap and 0 if there isn’t. When there is an overlap, the coordinates of the first and last pixels of the overlap will be put in

`fpixel_o`

and`lpixel_o`

.

Next: Polygons, Previous: Tessellation library, Up: Gnuastro library [Contents][Index]

JavaScript license information

GNU Astronomy Utilities 0.15 manual, May 2021.