An alternative form for the subscript expression involves specifying the centre and extent of the region required along each dimension, as follows:
q, r
s, ... )
where `pq', `r
s', (etc.) specify the
centre and extent. Thus,
11,200
5)
would refer to an 11 x 5 pixel region of an image centred on pixel (100, 200).
If the value before the delimiting `' is omitted, it will default to the
index of the central pixel in that dimension (rounded downwards if there are an
even number of pixels). If the value following the `
' is omitted, it will
default to the number of pixels in that dimension. Thus,
100,
100)
could be used to refer to a 100 x 100 pixel region located centrally within an image, while
, 20
)
would specify a section which is the same size as the original image, but displaced so that it is centred on pixel (10, 20).