II. DIGITAL IMAGES ANALYSIS AND PROCESSING
A digital image is a representation of a two-dimensional
image, defined as a finite set of digital values, named image
elements or pixels. The digital image consists of a fixed number of pixel lines and columns. Pixels represent the
smallest informational units of an image (usually associated
with small dots) which contain quantifiable values for
brightness and for the image dots. Normally, pixels are
stored in memory as a two-dimensional matrix of integer
values of type small. These values are sent or stored in a
compressed way.
Each pixel in an image is associated to a specific
position in a two-dimensional area. It has a specific numeric
value quantifying the image features (brightness, grey
shades or color information) that define the corresponding
image dot. Therefore, the digital images may be classified
according to the number and the nature of these samples:
binary, grayscale, false-color, multi spectral, thematic,
graphical functions.
Even if the term “texture” refers to the properties
belonging to the external surfaces of the objects and to the
sensations induced by touch, it is sometimes used to
describe non-tactile sensations. Also, the textures may
represent sub-dimensioned models (especially in case of
non-tactile two-dimensional textures), where the individual
elements are placed one next to the other, in order to
generate undistinguishable models.
Color may be an integral part of the texture’s model, or it
may be applied separately. In this case, a repetitive model of
the texture may be used in a number of ways in computer
graphics: green for grass, blue for water, grey for concrete,
dark grey for nocturnal images, etc