Digital Picture Processing Research Articles

A Note on the Use of Local Min and Max Operations in Digital Picture Processing

Abstract : Shrinking and expanding operations on two-valued digital pictures are useful for noise removal, as well as for detecting dense regions and elongated parts of objects. For grayscale pictures, the analogs of shrinking and expanding are local MIN and MAX operations. These operations commute with thresholding; thus if they are applied to a grayscale picture, followed by thresholding, the result is the same as if the picture were first thresholded and shrinking and expanding were then performed. Applying MIN and MAX operations prior to thresholding thus makes it possible to defer the choice of a threshold, which may be easier to select after these operations have been performed.

Instrument for the monochromatic observation of all sky auroral images

To investigate the dynamics of auroras and faint upper atmospheric emissions, a new type of imaging instrument was developed. The instrument is a wide field of view, narrow-spectral-band imaging system using an intensified S.E.C. TV camera in a time exposure mode. Pictures were taken at very low light levels of a few photons per exposure per resolution element. These pictures are displayed in the form of a pseudocolor presentation in which the color represents spectral ratios of two of the observed auroral spectral emission features. The spectral ratios play an important part in the interpretation of auroral particle dynamics. A digital picture processing facility is also part of the system which enables the digital manppulation of the pictures at standard TV rates. As an example, hydrogen auroras can be displayed having been corrected for nonspectral background by subtracting a picture obtained by a suitable background filter. The instrumentation was calibrated in the laboratory and was used in several field xperiments. Elaborate exposure sequences were developed to extend the dynamic range and to cover the large range of auroral brightnesses in a fairly linear manner.

Digital picture processing techniques for the publishing industry

This paper describes experimental digital methods for processing continuous tone pictures to produce outputs which are suitable for conventional printing methods. Digital halftone and line conversion techniques are discussed, and the results of both methods are shown.

A language for two-dimensional digital picture processing

A new system, that of matrix grammars, for two-dimensional pattern processing, is introduced. A hierarchy, induced on Chomsky's is found. Language operations such as union, catenation (row and column), Kleene's closure (row and column), and homomorphisms are investigated. It is found that the smallest class of these languages may serve as the class of regular arrays, which is defined as the smallest class of arrays closed under union, catenation (row and column) and Kleene's closure (row and column). Eight possible ways of defining a matrix language are discussed and it is suggested that one of them may lead to a normal form for matrix grammars. The method is advantageous over others on several points. Perhaps the most interesting of all is that it provides a compromise between sequential methods which take too much time for large arrays and parallel methods which usually take too much hardware for large arrays.

A language for two-dimensional digital picture processing

A new system, that of matrix grammars, for two-dimensional pattern processing, is introduced. A hierarchy, induced on Chomsky's is found. Language operations such as union, catenation (row and column), Kleene's closure (row and column), and homomorphisms are investigated. It is found that the smallest class of these languages may serve as the class of regular arrays, which is defined as the smallest class of arrays closed under union, catenation (row and column) and Kleene's closure (row and column). Eight possible ways of defining a matrix language are discussed and it is suggested that one of them may lead to a normal form for matrix grammars. The method is advantageous over others on several points. Perhaps the most interesting of all is that it provides a compromise between sequential methods which take too much time for large arrays and parallel methods which usually take too much hardware for large arrays.

Sequential Operations in Digital Picture Processing

Sequential Operations in Digital Picture Processing