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Digital image is representation of image as a finite set of
Digital image processing focuses on two major
tasks, i.e., improvement of pictorial information for human
interpretation and processing of image data for
storage, transmission and representation for autonomous
Components of DIP consist of image
sensor, digitizer, processor and display unit.
The key stages of DIP consist of Image Enhancement, Image
Restoration, Image Compression and Registration.
Image Registration is a process of mapping between temporal
sequences of image frames & covers Geometric
Transformation & Stereo imaging.
A digital image is a representation of a two-dimensional image as a finite set
of digital values, called picture elements or pixels.
Pixel values typically represent gray levels, colors, heights, opacities etc.
Digitization implies that a digital image is an approximation of a real scene.
The process of receiving and analyzing visual
information by digital computer is called digital image
Important Stages of Digital image processing are,
Discretization and representation
Image sensor:An image sensor intercepts the radiant
energy propagating the scene, and
transformations it to produce an
2. Digitizer:- A digitizer is required input images to a digital
produces digital image composed of discrete
values at discrete positions.
3. Processor :- Systems ranging from microcomputers to
large computers are used in image
4. Display unit :- A display device produces and shows a
visual form of numerical values stored in a computer as
image array. Principal display devices are printer, TV monitor
Whenever an image is converted from one form to
another, such as digitization, transmitting, scanning some
form of degradation occurs at the output.
Contrast intensification:One of the most common defects found in
the recorded image is its poor contrast. This degradation
may be caused by inadequate lighting, aperture
size, shutter speed and/or non linear mapping of the
2. Smoothing:Smoothing operation is used primarily to diminish the
effect of spurious noise and to blur the false contours
that may be present in a digital image.
Image Sharpening:Image degradation generally involves blurring.
Being an integration operation blurring attenuates high
spatial frequency components which suggests that
observed/ recoded image can be enhanced by
differentiation in spatial domain.
4. Image Restoration:One of the major application areas of image
processing technique is improving the quality of
5. Image Compression:Users of digital image processing
techniques usually have to handle a large volume of
data. Storing image data for future use needs large
storage space. Similarly transmitting image data in
reasonable time needs wide channel capacity.
Astronomy and space application.
Digital image processing enables the enhancement of visibility for
detail in images using algorithms that apply arithmetic and
statistical procedures to stored pixel values, instead of the classical
darkroom manipulations for filtration of time-dependent voltages
necessary for analog images and video signals.
Even though many image processing algorithms are extremely
powerful, the average user often applies operations to digital images
without concern for the underlying principles behind these
The images that result from careless manipulation are often severely
degraded or otherwise compromised with respect to those that
could be produced if the power and versatility of the digital
processing software were correctly utilized
“Digital Image Processing”, Rafael C. Gonzalez &
Richard E. Woods, Addison-Wesley, 2002