4.0 IMAGE PROCESSING FUNCTIONS, TECHNIQUES USED AND SYSTEM 
CONFIGURATIONS 
4.1 Image Processing Functions 4. 
Data acquisition, ground truth measurements, data processing 
and data management are some of the important aspects for effective 
utilization of remote sensing technology. The image processing 
functions can be broadly categorised as: 
- data format manipulations 
- radiometric restorations 
- image enhancement 
- image compression (de-compression) 
- pattern recognition 
- image annotation 
- image computations 
4.2 Techniques 
To meet the image processing functions described just now, a 
number of techniques have been developed. Until recently, these 
techniques used either complex analog circuits or off-line digital 
computers. However, it is now practical to do the processing in real 
time using video-rate image processing system. Some of these tech- 
niques are described below: 
(i) Shading correction for opto-electronics devices and sensors. 
(ii) Image manipulation such as addition, subtraction, multiplica - 
tion, inversion, rotation, cycling, zooming etc. 
(iii) Contrast modifications in linear, logarithmic, 
exponential, and non-linear form. 4,1 
(iv) Histogram generation, equalization, level slicing, colour 
encoding, pseudo-colour generation. 
(v) Transform coding techniques such as Walsh Hadamard slant and 
others, 
(vi) Convolutions Kernels, spatial filtering, Gaussian and Lapalacian, 
logarithmic filtering, image smoothing, image band width 
compression and de-compression. 
(vii) Correlation and auto-correlation functions. 
(vii) Graphic generation, gridding, labeling, outlining, generating 
arbitrary shaped images, image mixing, splits, overlay and 
annotation. 
(ix) Image parameter computations and measurement. 
4.3 System Configurations 
A number of image processing systems are now commercially 
available which can carpy out a combination of these techniques on real 
time basis. A typical video-rate image processing system which carries 
out a variety of image processing functions will consist of the following 
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