1. IT523 Digital Image Processing
Prof. Asim Banerjee
Lecture 3
6th August 2007

2. 1. Improvement … Human Interpretation
Involves selection of printing procedures and distribution of brightness levels
Improvements on processing methods for transmitted digital pictures
Application areas include
Archeology
Astronomy
Biology
Industrial Applications
Law enforcements
Medical Imaging
Space program etc.
IT523 - Digital Image Processing

3. 2. Processing…Machine Perception
Focuses on procedures for extracting from an image information in a form suitable for computer processing
NOTE : Often this information bears little resemblance to visual features that human beings use in interpreting the content of an image.
Application areas include:
Automatic Optical Character Recognition
Machine vision for product assembly and inspection
Military recognizance
Automatic fingerprint matching etc.
IT523 - Digital Image Processing

4. Structure of The Human Eye
IT523 - Digital Image Processing

5. IT523 - Digital Image Processing
Elements of HVP (1/2)
Structure of the human eye
Comprises of the cornea and sclera outer cover, the choroid and the retina
Image formation in the eye
The light from the object passes through the flexible lens
The image is formed on the retina of the eye
Brightness adaptation
The range of intensity levels to which the system can adapt is enormous (~1010)
Subjective brightness is a logarithmic function of the light intensity incident on the eye
IT523 - Digital Image Processing

6. IT523 - Digital Image Processing
Elements of HVP (2/2)
Brightness discrimination
The total range of intensity levels the eye can discriminate simultaneously is rather small compared to the total adaptation range
Ability to discriminate between two intensity values is not a simple function of intensity
The visual system tends to undershoot or overshoot around boundary of regions of different intensities
A region’s perceived brightness also depends on the intensity level of the surrounding region (simultaneous contrast)
IT523 - Digital Image Processing

7. IT523 - Digital Image Processing

8. Simultaneous Contrast
The gray level of the square in the center is the same in all the images
IT523 - Digital Image Processing

9. IT523 - Digital Image Processing
Assignment #1
Find out about the properties of the human visual system and state the possible usage of these properties in building DIP systems.
Submit by: 5:00 p.m. on Monday (13th August 2007).
IT523 - Digital Image Processing

10. The Digital Image Processing System
Recognition and Interpretation
Outside world
O/P
Preprocessing
Knowledge Base
Segmentation
Representation and Description
Image Acquisition
The Digital Image Processing System
The DIP system takes inputs from the outside world and produces desirable (application dependent) outputs.
IT523 - Digital Image Processing

11. IT523 - Digital Image Processing
Image Acquisition (1/2)
Two elements are required to acquire a digital image
A physical device that is sensitive to a band in the electromagnetic spectrum (X-ray, Ultra Violet, Visible, Infrared) to produce an electrical signal proportional to the level of energy sensed (i.e. sensors or detectors)
A digitizer to convert this signal into digital form.
NOTE: There are sensors available that directly give digital output.
IT523 - Digital Image Processing

12. IT523 - Digital Image Processing
Image Acquisition (2/2)
IT523 - Digital Image Processing

13. IT523 - Digital Image Processing
Preprocessing
It improves the image in ways that increase the chances of success for the other processes
For example
Enhancing contrast
Removing noise
Isolating regions of interest (ROI).
IT523 - Digital Image Processing

14. IT523 - Digital Image Processing
Segmentation
It partitions an input image into its constituent parts or objects.
NOTE:
Autonomous segmentation is one of the most difficult tasks in digital image processing.
Good segmentation ensures ease in achieving successful solution to an imaging problem.
Bad segmentation guarantee eventual failure to an imaging problem.
IT523 - Digital Image Processing

15. Representation & Description
Representation implies conversion of the data to a form suitable for computer processing e.g. boundary representation or complete region representation.
Description (or feature selection) deals with extracting features that result in some quantitative information of interest or features that can differentiate one class of objects from another.
IT523 - Digital Image Processing

16. Recognition & Interpretation
Recognition implies assigning of a label to an object based on information provided by its descriptors
Interpretation implies assigning of a meaning to an ensemble of recognized objects.
IT523 - Digital Image Processing

17. IT523 - Digital Image Processing
Image Knowledgebase
The knowledgebase stores the prior knowledge about the outside world (the problem domain)
The processing modules interact with the knowledgebase to aid in the processing.
IT523 - Digital Image Processing

18. Elements of DIP System (1/3)
Image acquisition
Scanners, video camera, CCD cameras, digitizers, etc.
Storage
Short term storage, on-line storage and archival storage
Processing
Small personal computers to dedicated processing hardware.
IT523 - Digital Image Processing

19. Elements of DIP System (2/3)
Communication
Local communication between the processing systems
Remote communication for transmission of images
Display
Monochrome Monitors to sophisticated display devices
IT523 - Digital Image Processing

20. Elements of DIP System (3/3)
IT523 - Digital Image Processing

21. Image Sensing & Acquisition (1/4)
The images of interest are those generated by the combination of
An illumination source and
And the reflection or absorption of the energy from that source by the elements of the scene being imaged.
The principal arrangements of the detectors or sensors are:
Single imaging sensor
Line sensor
Array sensor.
IT523 - Digital Image Processing

22. Image Sensing & Acquisition (2/4)
IT523 - Digital Image Processing

23. Image Sensing & Acquisition (3/4)
IT523 - Digital Image Processing

24. Image Sensing & Acquisition (3/4)
IT523 - Digital Image Processing

25. IT523 - Digital Image Processing
That’s all for now.
IT523 - Digital Image Processing