Showing papers on "Grayscale published in 1977"

A Note on the Use of Second-Order Gray Level Statistics for Threshold Selection.

Abstract: : The gray level histogram of an image is commonly used as an aid in selecting thresholds for segmenting the image Various methods have been proposed to make threshold selection easier This note describes a class of such methods that make use of second-order gray level statistics to define improved histograms (Author)

Method and apparatus for reproducing an original gray scale image

Abstract: A method and apparatus are disclosed for reproducing an original gray scale image that may be divided into an array of discrete picture elements. The method comprises the steps of scanning each of the picture elements in the array on the original image to determine its gray level and location in the array and generating sequential signals that contain data indicative of the gray level and location in the array of each of the scanned picture elements. The gray level of the entire array is calculated from the data on each of its individual picture elements in accordance with a gray scale function. On a reproduction medium in an array of reproduction locations corresponding to the picture element array, locations are sequentially darkened in order of decreasing gray level, beginning at the location that corresponds to the scanned picture element having the darkest gray level, until the gray level of the reproduction array substantially equals the calculated gray level of the scanned picture element array. Therefore, the gray level distribution of the picture element array is substantially duplicated on the reproduction array to provide maximum resolution within the capability of the scanning and darkening systems. In addition, this method reduces the amount of data processed in order to reproduce maximum image resolution. The apparatus for performing this method comprises various components for performing each of its steps.

Digital circuit for accurately detecting changes in the gray scale of a scanned image

Abstract: A digital circuit for detecting changes in the gray scale of scanned images is disclosed. Each line of video information produced by scanning the image is digitized. Each digital sample is compared to digital samples delayed a predetermined amount to generate a difference signal which is indicative of a change in the gray scale having a component perpendicular to the direction of scan. The digitized samples of the video signal are also stored in a memory having a capacity sufficient to store data representing a plurality of scan lines with a typical memory having a capacity for storing digital information representing eight scan lines. Selected digital samples from the stored data are compared to samples of the line being scanned to detect changes in the gray scale having a component parallel to the direction of scan. These changes in the gray scale are combined to generate a signal indicative of the central portion of the change in the gray scale of the image being scanned to drive a printer to generate a line drawing with the position of the lines corresponding to the central portion of the changes in gray scale of the scanned image.

Display method and apparatus

Abstract: A method of displaying image data is provided, which includes analyzing histograms by color signals of an input image frame; confirming grayscales by color signals in a predetermined frame unit with reference to the analyzed histograms; determining dimming factors in consideration of maximum grayscale values of the grayscales; determining image gains of the image data by color signals using the determined dimming factors; and outputting an image signal by applying the image gains to the input image and applying the dimming factors to a light source.

Use of Spatial Filtering to Match Wide Dynamic Range Grayscale Imagery to a Lower Resolution Display

Abstract: : We investigate the ability of nonlinear spatial filtering to reduce the amount of information that is lost when a display device has a lower dynamic range than the grayscale imagery to be displayed on it. Dynamic range compression can be achieved by attenuating an assumed low-frequency multiplicative background and enhancing higher frequencies using homomorphic filtering. This technique, originally described by Oppenheim for images formed by reflection of visible light, is extended to images formed by emission of IR radiation and transmission of X-ray and gamma-ray radiation. Examples are given which show dynamic range compression of the three types of images achieved by means of a homomorphic filtering and display procedure having no free parameters which must be optimized to suit the particular input image. (Author)