FITS square pixel grid (15x15), in blue
FITS (Flexible Image
Transport System) is the IAU standard for data interchange in
Data values in a FITS image array occupy a regular N-dimensional
Ordered so that the first axis varies fastest (FORTRAN order).
Best thought of as an array of delta sampling functions on a square
For display purposes
Delta functions are represented as finite-sized, square
pixels (not rectangular or hexagonal).
By convention, the first pixel is at lower-left, increasing to the
right, then upwards.