Coregistered Lunar Orbiter and Clementine color-ratio mosaics
of the Rima Bode region of the Moon (LO-IV 109H2).
From the "Lunar Orbiter Digitization Project" @ astrogeology.usgs.gov
.
An image is obtained from:
a camera
scanned from an existing print
produced via a graphics engine
An image can be tought of as a 2D density field, f(x,y), where each
locus (point (x,y)) in the field (typically a rectangular area) takes
on a value or set of values:
binary field: black or white, f(x,y) = 0's or 1's
grey-level field: shades of grey from black to white,
f(x,y) = g (e.g., 0 <= g
<= 128)
color field: multiple color values for each locus
(typically: 3 values, like red, green, blue)
A digital image is an
image which is both quantized
and sampled:
The density field values are quantized: a continuous range of
light intensities is mapped to a discrete set of values (e.g., integers between 0 and 128).
The 2D spatial layout is represented via a Cartesian
grid, where grid nodes represent coordinates with integer values: e.g.,
x = [0,...,100], y = [0,...,200]
Sampling of a 2D binary image
The end result is a matrix of values (grey or (r,g,b))
where each (x,y) locus represent a uniform quantized value in the form
of a pixel (or picture
element).
