DIGITAL IMAGE PROCESSING INTRODUCTION
Pictures are the most common and convenient means of conveying or transmitting information. A picture is worth a thousand words. Pictures concisely convey information about positions, sizes and inter-relationships between objects. They portray spatial information that we can recognize as objects. Pictures concisely convey information about positions, sizes and inter-relationships between objects. They portray spatial information that we can recognize as objects.Human beings are good at deriving information from such images, because of our innate visual and mental abilities. About 75% of the information received by human is in pictorial form.
A digital image is typically composed of picture elements (pixels) located at the intersection of each row i and column j in each K bands of imagery.Each pixel is associated a number known as Digital Number (DN) or Brightness Value (BV), that depicts the average radiance of a relatively small area within a scene (Fig. 1)
A smaller number indicates low average radiance from the area and the high number is an indicator of high radiant properties of the area .
While displaying the different bands of a multispectral data set, images obtained in different bands are displayed in image planes (other than their own) the color composite is regarded as False Color Composite (FCC). A color infrared composite Ëœstandard false color compositeâ„¢ is displayed by placing the infrared, red, green in the red, green and blue frame buffer memory (Fig. 2).
Geometric distortions manifest themselves as errors in the position of a pixel relative to other pixels in the scene and with respect to their absolute position within some defined map projection. If left uncorrected, these geometric distortions render any data extracted from the image useless
REASONS OF DISTORTIONS
For instance distortions occur due to...