12-08-2011, 03:15 PM
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Introduction to Digital image processing
Types of image –Monochrome image, Gray scale image, color image(24) bit , half toned image.
Color image processing
Scene splitting
Morphology
Advantage and disadvantage of digital image processing.
What is image??
Two dimensional representation of three dimensional world is called as image.
The missing dimension in an image is basically the depth.
Most of cameras use for imaging is sensitive to this range of electro magnetic spectrum(380-760nm).
Although even there are cameras which are capable of detecting infrared,ultravoilet light,x-rays and radio waves too.
What is image processing??
Image processing is an integral part of human being and one continue to process image sub consciously doing this every now and then.
The human eye –brain mechanism represents the ultimate imaging system
BASIC ELEMENTS OF IMAGE PROCESSING SYSTEM
Digital image processing is modification images on a computer. The components involved in this process are -
Image acquisition
Image storage
Image processing
Display
Transmission(if required)
Image acquisition
It is the first step in any image processing system
The general aim of image acquisition is to transform an optical image (real world data) into an array of numerical data which could be later manipulated on a computer
Image acquisition is achieve by suitable camera depending upon the image requirement
IMAGE STORAGE
All video signals are essentially in analog form that is electrical signal convey luminance and color with continuously variable voltage.
The cameras are interfaced to a computer where the processing algorithm are written from grabber card.
Usually a frame grabber card is a PCB fitted to host computer with its analog entrance port matching the impedance of incoming video signal.
Frame grabber card usually have A/D card with resolution of 8 to 12 bits.
Frame grabber has a block of memory – frame buffer memory – large capacity .
Image data 8 bit – written under computer control- by DMA transfer. And contents are read out at a video rate 30 frames per second pass through D/A converter and displayed monitor.
Table representing amount of space required to store an image
Image processing
System ranging from microcomputer to general purpose large computer are used in image processing
Processing of digital image involve procedure that are usually expressed in algorithm form due to which most image processing are implemented on software .
Display
A display device produces and shows a visual form of numerical values store in a computer as an image array .
Principal display devices- printer, T.V., monitor CRT .
Monochrome and color tv monitors-principal display devices used in modern image processing system.
These raster devices convert image data into video frame
Stages of transmission
Transmission
The image sequence from camera is coded into as concise a representation as possible for transmission over the channel.
NTSE,PAL and SECAM are the three major coding system used in various parts of the world.
USA uses NTSE while INDIA uses PAL.
TYPES OF IMAGES
As images are two dimensional function they can be classified as follows:
Monochrome images
Gray scale images
Color (24bit) images
Half –toned images
Monochrome images
In this each pixel is stored as a single bit.
Here 0 represents black while 1 represent white.
It is black and white image in the strictest sense.
The images are also called bit mapped images.
In such images we have black and white pixel and no other shades of grey.
MONOCHROME IMAGE
GREY SCALE IMAGES
Here each pixel is usually stored as a byte (8 bits).
Due to this each pixel can have value ranging from 0(black) to 255(white).
GRAY SCALE IMAGE
COLOR IMAGES(24 bits)
They are based on the fact that a variety of colors can be generated by mixing three primary colors viz, Red,Green,Blue in proper proportions
In this each pixel is composed of RGB value and each of these required 8 bits for its representation.
Hence each pixel is represented by 24 bits .
A 24 bit color image supports 16 , 777,216 different combinations of colors .
COLOR (24) BIT IMAGE
Half toned images
The emergence of half tonning of images is due to the following reason-
Instead of the better picture quality shown by grey scale images they suffer a drawback that they are not easily compatible to various ink jet ,laser and dot matrix printers.
This is due to the fact that they all are bi level devices ie they show only two colours ie black on white backgrounds.
This is not at all ideal for the case that one has to get the entire proper image.
HALF TONED IMAGE
Color image processing
The retina in eye is covered with photo receptor cells(rods and cones).
Rods provide us with monochromatic night vision while cones are responsible for color vision.
There are about 6 to 7 million cones in the human eye.
The cones occur in three types, differing mainly
in photochemistry they employ to convert light into nerve impulses. The cone divides visible portion of the electromagnetic spectrum into three bands viz Red,Green andBlue.These three color are hence called primary colors
SCENE SPLITTING
The color TV, camera TV consist of three camera tubes
Each of these three cameras receives a filtered primary color .
The light from the scene split up into three primary color by using three prisms
These prisms are designed as diachronic mirror
It passes only one wavelength.
The rays from these mirror is now pass through color filters known as trimming filter
These are covered to video signals by red, green and blue camera tube
Morphology
Morphology is a science of form and structure
In the strict sense , denotes a branch of biology the deals with structure of animals and plants
In image processing morphology is about regions and shape.
Morphological techniques treat an image as an assemble of sets
Morphology can hence be defined as interaction between two sets-
Advantages & disadvantages of digital image processing
Advantage
• High noise immunity
• Adjustable precision
• Ease of design (automation) and
• Fabrication, therefore, low cost
• Better Reliability
• Less need for calibration and maintenance
• Ease of diagnosis and repair
• Easy to duplicate similar circuits
• Easily controllable by computer
Disadvantage
• Lower speed
• Needs converters to communicate with
real world, therefore , f m p more expensive
and less precision
– Digital to Analog (D/A)
– Analog to Digital (A/D)
Introduction to Digital image processing
Types of image –Monochrome image, Gray scale image, color image(24) bit , half toned image.
Color image processing
Scene splitting
Morphology
Advantage and disadvantage of digital image processing.
What is image??
Two dimensional representation of three dimensional world is called as image.
The missing dimension in an image is basically the depth.
Most of cameras use for imaging is sensitive to this range of electro magnetic spectrum(380-760nm).
Although even there are cameras which are capable of detecting infrared,ultravoilet light,x-rays and radio waves too.
What is image processing??
Image processing is an integral part of human being and one continue to process image sub consciously doing this every now and then.
The human eye –brain mechanism represents the ultimate imaging system
BASIC ELEMENTS OF IMAGE PROCESSING SYSTEM
Digital image processing is modification images on a computer. The components involved in this process are -
Image acquisition
Image storage
Image processing
Display
Transmission(if required)
Image acquisition
It is the first step in any image processing system
The general aim of image acquisition is to transform an optical image (real world data) into an array of numerical data which could be later manipulated on a computer
Image acquisition is achieve by suitable camera depending upon the image requirement
IMAGE STORAGE
All video signals are essentially in analog form that is electrical signal convey luminance and color with continuously variable voltage.
The cameras are interfaced to a computer where the processing algorithm are written from grabber card.
Usually a frame grabber card is a PCB fitted to host computer with its analog entrance port matching the impedance of incoming video signal.
Frame grabber card usually have A/D card with resolution of 8 to 12 bits.
Frame grabber has a block of memory – frame buffer memory – large capacity .
Image data 8 bit – written under computer control- by DMA transfer. And contents are read out at a video rate 30 frames per second pass through D/A converter and displayed monitor.
Table representing amount of space required to store an image
Image processing
System ranging from microcomputer to general purpose large computer are used in image processing
Processing of digital image involve procedure that are usually expressed in algorithm form due to which most image processing are implemented on software .
Display
A display device produces and shows a visual form of numerical values store in a computer as an image array .
Principal display devices- printer, T.V., monitor CRT .
Monochrome and color tv monitors-principal display devices used in modern image processing system.
These raster devices convert image data into video frame
Stages of transmission
Transmission
The image sequence from camera is coded into as concise a representation as possible for transmission over the channel.
NTSE,PAL and SECAM are the three major coding system used in various parts of the world.
USA uses NTSE while INDIA uses PAL.
TYPES OF IMAGES
As images are two dimensional function they can be classified as follows:
Monochrome images
Gray scale images
Color (24bit) images
Half –toned images
Monochrome images
In this each pixel is stored as a single bit.
Here 0 represents black while 1 represent white.
It is black and white image in the strictest sense.
The images are also called bit mapped images.
In such images we have black and white pixel and no other shades of grey.
MONOCHROME IMAGE
GREY SCALE IMAGES
Here each pixel is usually stored as a byte (8 bits).
Due to this each pixel can have value ranging from 0(black) to 255(white).
GRAY SCALE IMAGE
COLOR IMAGES(24 bits)
They are based on the fact that a variety of colors can be generated by mixing three primary colors viz, Red,Green,Blue in proper proportions
In this each pixel is composed of RGB value and each of these required 8 bits for its representation.
Hence each pixel is represented by 24 bits .
A 24 bit color image supports 16 , 777,216 different combinations of colors .
COLOR (24) BIT IMAGE
Half toned images
The emergence of half tonning of images is due to the following reason-
Instead of the better picture quality shown by grey scale images they suffer a drawback that they are not easily compatible to various ink jet ,laser and dot matrix printers.
This is due to the fact that they all are bi level devices ie they show only two colours ie black on white backgrounds.
This is not at all ideal for the case that one has to get the entire proper image.
HALF TONED IMAGE
Color image processing
The retina in eye is covered with photo receptor cells(rods and cones).
Rods provide us with monochromatic night vision while cones are responsible for color vision.
There are about 6 to 7 million cones in the human eye.
The cones occur in three types, differing mainly
in photochemistry they employ to convert light into nerve impulses. The cone divides visible portion of the electromagnetic spectrum into three bands viz Red,Green andBlue.These three color are hence called primary colors
SCENE SPLITTING
The color TV, camera TV consist of three camera tubes
Each of these three cameras receives a filtered primary color .
The light from the scene split up into three primary color by using three prisms
These prisms are designed as diachronic mirror
It passes only one wavelength.
The rays from these mirror is now pass through color filters known as trimming filter
These are covered to video signals by red, green and blue camera tube
Morphology
Morphology is a science of form and structure
In the strict sense , denotes a branch of biology the deals with structure of animals and plants
In image processing morphology is about regions and shape.
Morphological techniques treat an image as an assemble of sets
Morphology can hence be defined as interaction between two sets-
Advantages & disadvantages of digital image processing
Advantage
• High noise immunity
• Adjustable precision
• Ease of design (automation) and
• Fabrication, therefore, low cost
• Better Reliability
• Less need for calibration and maintenance
• Ease of diagnosis and repair
• Easy to duplicate similar circuits
• Easily controllable by computer
Disadvantage
• Lower speed
• Needs converters to communicate with
real world, therefore , f m p more expensive
and less precision
– Digital to Analog (D/A)
– Analog to Digital (A/D)
