06-02-2012, 02:37 PM
DIGITAL IMAGE PROCESSING
ABSTRACT
This paper describes the basic technological aspects of Digital Image Processing with special reference to sampling, quantization, histogram, gray scale images. The digital image processing technique is used to convert defocused, blurred image to clear image. The former deals with initial processing of raw image data to correct for geometric distortion, to calibrate the data radio metrically and to eliminate noise present in the data. The enhancement procedures are applied to image data in order to effectively display the data for subsequent visual interpretation. It involves techniques for increasing the visual distinction between features in a scene. The objective of the information extraction operations is to replace visual analysis of the image data with quantitative techniques for automating the identification of features in a scene. The intent of classification process is to categorize all pixels in a digital image into one of several land cover classes or themes. This classified data may be used to produce thematic maps of the land cover present in an image.
INTRODUCTION
Digital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and signal distortion during processing. Since images are defined over two dimensions (perhaps more) digital image processing may be modeled in the form of Multidimensional Systems.
DIGITAL IMAGE PROCESSING
Many types of remote sensing images are routinely recorded in digital form and then processed by computers to produce images for interpreters to study. The simplest form of digital image processing employs a microprocessor that converts the digital data tape into a film image with minimal corrections and calibrations. At the other extreme, large mainframe computers are employed for sophisticated interactive manipulation of the data to produce images in which specific information has been extracted and highlighted.
DIGITAL IMAGE PROCESSING TECHNIQUES
Digital processing did not originate with remote sensing and is not restricted to these data. Many image-processing techniques were developed in the medical field to process X-ray images and images from sophisticated body-scanning devices. For remote sensing, the initial impetus was the program of unmanned planetary satellites in the 1960s that telemetered or transmitted, images to ground receiving stations .For remote sensing, the initial impetus was the program of unmanned planetary satellites in the 1960s that telemetered, or transmitted, images to ground receiving stations.
The low quality of the images required the development of processing techniques to make the images useful. Another impetus was the Land sat program, which began in 1972 and provided repeated worldwide coverage in digital format.
A third impetus is the continued development of faster and more powerful computers, peripheral equipment, and software that are suitable for image processing.
IMAGE-PROCESSING OVERVIEW
Image restoration compensates for data errors, noise, and geometric distortions introduced during the scanning, recording, and playback operations. Restoring periodic line dropouts, Restoring periodic line striping, Filtering of random noise, Correcting for atmospheric scattering, Correcting geometric distortions. Image enhancement alters the visual impact that the image has on the interpreter in a fashion that improves the information content. Contrast enhancement, Intensity, hue, and saturation transformations, Density slicing, Edge enhancement, Making digital mosaics, Producing synthetic stereo images. Information extraction utilizes the decision-making capability of the computer to recognize and classify pixels on the basis of their digital signatures. Producing principal-component images, Producing ratio images, Multispectral classification, Producing change-detection images.
