1.1 DIGITAL IMAGE FUNDAMENTALS - INTRODUCTION
Introduction
Signal processing is a discipline in electrical engineering and in mathematics that deals with
analysis and processing of analog and digital signals , and deals with storing , filtering , and
other operations on signals. These signals include transmission signals , sound or voice signals
, image signals , and other signals e.t.c.
Out of all these signals , the field that deals with the type of signals for which the input is an
image and the output is also an image is done in image processing. As it name suggests, it deals
with the processing on images.
It can be further divided into analog image processing and digital image processing.
Analog image processing
Analog image processing is done on analog signals. It includes processing on two dimensional
analog signals. In this type of processing, the images are manipulated by electrical means by
varying the electrical signal. The common example include is the television image.
Digital image processing has dominated over analog image processing with the passage of time
due its wider range of applications.
What is an Image
An image is defined as a two-dimensional function F(x,y) where x and y are spatial coordinates
and the amplitude of F at any pair of coordinates (x,y) is called the intensity of that image at
that point. When x, y and amplitude values of F are finite, we call it a digital image.
An image is nothing more than a two dimensional signal. It is defined by the mathematical
function f(x,y) where x and y are the two co-ordinates horizontally and vertically.
The value of f(x,y) at any point is gives the pixel value at that point of an image.
,The above figure is an example of digital image that you are now viewing on your computer
screen. But actually , this image is nothing but a two dimensional array of numbers ranging
between 0 and 255.
128 30 123
232 123 321
123 77 89
80 255 255
Each number represents the value of the function f(x,y) at any point. In this case the value 128
, 230 ,123 each represents an individual pixel value. The dimensions of the picture is actually
the dimensions of this two dimensional array.
Digital image processing
Digital Image Processing is a software which is used to manipulate the digital images by the
use of computer system. It is also used to enhance the image, to get some important information
from it.
The digital image processing deals with developing a digital system that performs operations
on an digital image.
Relationship between a digital image and a signal
If the image is a two dimensional array then what does it have to do with a signal? In order to
understand that , We need to first understand what is a signal?
,Signal
In physical world, any quantity measurable through time over space or any higher dimension
can be taken as a signal. A signal is a mathematical function, and it conveys some information.
A signal can be one dimensional or two dimensional or higher dimensional signal. One
dimensional signal is a signal that is measured over time. The common example is a voice
signal.
The two dimensional signals are those that are measured over some other physical quantities.
The example of two dimensional signal is a digital image. We will look in more detail in the
next tutorial of how a one dimensional or two dimensional signals and higher signals are
formed and interpreted.
Relationship
Since anything that conveys information or broadcast a message in physical world between
two observers is a signal. That includes speech or (human voice) or an image as a signal. Since
when we speak , our voice is converted to a sound wave/signal and transformed with respect
to the time to person we are speaking to. Not only this , but the way a digital camera works, as
while acquiring an image from a digital camera involves transfer of a signal from one part of
the system to the other.
How a digital image is formed
Since capturing an image from a camera is a physical process. The sunlight is used as a source
of energy. A sensor array is used for the acquisition of the image. So when the sunlight falls
upon the object, then the amount of light reflected by that object is sensed by the sensors, and
a continuous voltage signal is generated by the amount of sensed data. In order to create a
digital image , we need to convert this data into a digital form. This involves sampling and
quantization. (They are discussed later on). The result of sampling and quantization results in
an two dimensional array or matrix of numbers which are nothing but a digital image.
Overlapping fields
Machine/Computer vision
, Machine vision or computer vision deals with developing a system in which the input is an
image and the output is some information. For example: Developing a system that scans human
face and opens any kind of lock. This system would look something like this.
Computer graphics
Computer graphics deals with the formation of images from object models, rather then the
image is captured by some device. For example: Object rendering. Generating an image from
an object model. Such a system would look something like this.
Artificial intelligence
Artificial intelligence is more or less the study of putting human intelligence into machines.
Artificial intelligence has many applications in image processing. For example: developing
computer aided diagnosis systems that help doctors in interpreting images of X-ray , MRI e.t.c
and then highlighting conspicuous section to be examined by the doctor.
Signal processing
Signal processing is an umbrella and image processing lies under it. The amount of light
reflected by an object in the physical world (3d world) is pass through the lens of the camera
Introduction
Signal processing is a discipline in electrical engineering and in mathematics that deals with
analysis and processing of analog and digital signals , and deals with storing , filtering , and
other operations on signals. These signals include transmission signals , sound or voice signals
, image signals , and other signals e.t.c.
Out of all these signals , the field that deals with the type of signals for which the input is an
image and the output is also an image is done in image processing. As it name suggests, it deals
with the processing on images.
It can be further divided into analog image processing and digital image processing.
Analog image processing
Analog image processing is done on analog signals. It includes processing on two dimensional
analog signals. In this type of processing, the images are manipulated by electrical means by
varying the electrical signal. The common example include is the television image.
Digital image processing has dominated over analog image processing with the passage of time
due its wider range of applications.
What is an Image
An image is defined as a two-dimensional function F(x,y) where x and y are spatial coordinates
and the amplitude of F at any pair of coordinates (x,y) is called the intensity of that image at
that point. When x, y and amplitude values of F are finite, we call it a digital image.
An image is nothing more than a two dimensional signal. It is defined by the mathematical
function f(x,y) where x and y are the two co-ordinates horizontally and vertically.
The value of f(x,y) at any point is gives the pixel value at that point of an image.
,The above figure is an example of digital image that you are now viewing on your computer
screen. But actually , this image is nothing but a two dimensional array of numbers ranging
between 0 and 255.
128 30 123
232 123 321
123 77 89
80 255 255
Each number represents the value of the function f(x,y) at any point. In this case the value 128
, 230 ,123 each represents an individual pixel value. The dimensions of the picture is actually
the dimensions of this two dimensional array.
Digital image processing
Digital Image Processing is a software which is used to manipulate the digital images by the
use of computer system. It is also used to enhance the image, to get some important information
from it.
The digital image processing deals with developing a digital system that performs operations
on an digital image.
Relationship between a digital image and a signal
If the image is a two dimensional array then what does it have to do with a signal? In order to
understand that , We need to first understand what is a signal?
,Signal
In physical world, any quantity measurable through time over space or any higher dimension
can be taken as a signal. A signal is a mathematical function, and it conveys some information.
A signal can be one dimensional or two dimensional or higher dimensional signal. One
dimensional signal is a signal that is measured over time. The common example is a voice
signal.
The two dimensional signals are those that are measured over some other physical quantities.
The example of two dimensional signal is a digital image. We will look in more detail in the
next tutorial of how a one dimensional or two dimensional signals and higher signals are
formed and interpreted.
Relationship
Since anything that conveys information or broadcast a message in physical world between
two observers is a signal. That includes speech or (human voice) or an image as a signal. Since
when we speak , our voice is converted to a sound wave/signal and transformed with respect
to the time to person we are speaking to. Not only this , but the way a digital camera works, as
while acquiring an image from a digital camera involves transfer of a signal from one part of
the system to the other.
How a digital image is formed
Since capturing an image from a camera is a physical process. The sunlight is used as a source
of energy. A sensor array is used for the acquisition of the image. So when the sunlight falls
upon the object, then the amount of light reflected by that object is sensed by the sensors, and
a continuous voltage signal is generated by the amount of sensed data. In order to create a
digital image , we need to convert this data into a digital form. This involves sampling and
quantization. (They are discussed later on). The result of sampling and quantization results in
an two dimensional array or matrix of numbers which are nothing but a digital image.
Overlapping fields
Machine/Computer vision
, Machine vision or computer vision deals with developing a system in which the input is an
image and the output is some information. For example: Developing a system that scans human
face and opens any kind of lock. This system would look something like this.
Computer graphics
Computer graphics deals with the formation of images from object models, rather then the
image is captured by some device. For example: Object rendering. Generating an image from
an object model. Such a system would look something like this.
Artificial intelligence
Artificial intelligence is more or less the study of putting human intelligence into machines.
Artificial intelligence has many applications in image processing. For example: developing
computer aided diagnosis systems that help doctors in interpreting images of X-ray , MRI e.t.c
and then highlighting conspicuous section to be examined by the doctor.
Signal processing
Signal processing is an umbrella and image processing lies under it. The amount of light
reflected by an object in the physical world (3d world) is pass through the lens of the camera
