Basic Function of SweepLine.py
You can provide the coordinates of points (Voronoi sites) in two ways, either in terms of a coordinates list or an image. If the input file has a suffix of ".fits", it is taken as a FITS format image. Or else, it is regarded as an ASCII plain-text file, which contains the coordinates of points in its first two columns.
For example the points are contained in the file "data.txt"
unix$ cat data.txt -0.5 1.5 1.1 3.3 2.9 5.7 3.1 4.3 5.4 2.6 6.3 3.1
Run SweepLine.py with "--makeimage" option, which tells SweepLine.py to generate an image which contains the input points, in order to check the result easily.
unix$ SweepLine.py data.txt --makeimage
The basic function of SweepLine.py is to construct the Voronoi diagram, which is composed of lines. The lines can be single-endpoint rays at the image border. However, SweepLine.py confines them to the box domain of the image. Therefore, all the lines have two endpoints, which are easy to plot in a figure. The lines which are described by four values (a pair of endpoints) are presented in a ds9 manner. In this example, Voronoi diagram is saved in "data.reg".
With the "--makeimage" option, two addition files "data_image.fits" and "data_points.reg" are generated, in order to visualize the result with ds9. The header of "data_image.fits" is as follows:
BITPIX = -64 / array data type NAXIS = 2 / number of array dimensions NAXIS1 = 8 NAXIS2 = 8 OFFSETX = 0.5 OFFSETY = 0
unix$ ds9 data_image.fits -region data_points.reg -region data.reg
The circles are the input points, however the coordinates are transfered from C-fromat to Fortran-format and shifted to the range of [0,imagesize].
X_input + OFFSETX + 1 = Y_ds9 Y_input + OFFSETY + 1 = X_ds9
"data_image.fits" is a 8x8 image, in which point positions are rounded to integers.
Then, use the "data_image.fits" as an input to show how the FITS-input mode works.
unix$ SweepLine.py data_image.fits unix$ ds9 data_image.fits -region data_image.reg
The pattern is different because the input Voronoi sites are different, which have integer positions.