Showing papers on "Grayscale published in 1976"

Apparatus and a method for storage and retrieval of image patterns

Abstract: A line image or a line signature is optically scanned to generate digital signals for storage in an image matrix. These digital signals represent black and white cells defining the line signature or line image and are initially processed by tracing the image boundary. During the tracing a "thinning" or "peeling off" operation is performed that evaluates black cells in the image matrix for conversion into white cell digital signals. This thinning or peeling off process, also identified as data compression, continues until the line signature or line image is composed of a single cell thickness. The final phase of the data compression operation includes another boundary tracing of the one cell thick image, and connecting a sequence of boundary points defining each black cell to form a string of vectors which represent the signature. The resulting vector catalog comprises a composition of data including a vector starting point and vector directions which are encoded and stored for future retrieval. When a stored line signature or line image is to be retrieved for display, the encoded vector data is recalled from storage to generate on a cathode ray tube the original vector data. This operation is known as data decompression and produces on the cathode ray tube a synthesis of the original line image or line signature. The compression and decompression operations, except thinning or peeling off, are also applicable to textured images or images having grayscale and thickness. Such textured images are first subdivided into binary images, each representing one bit of the grayscale, then the vector boundary encoding process is completed without thinning. The encoded vectors are stored for subsequent retrieval and display.

A New Technique for Displaying Continuous Tone Images on a Bilevel Display

Abstract: A new technique for the display of continuous tone images on a bilevel graphical output device is described. This technique belongs to the general class of algorithms that convey intensity information by the spatial arrangement of lit and unlit cells which are in a one-to-one correspondence with the picture elements (PEL's) in the original image. Besides the rendition of a gray scale in the processed image, the new algorithm also incorporates edge emphasis to increase the legibility of textual information and other areas of high detail. A simple theory of the algorithm, derived from an intensity distribution function, is given, along with the details of an implementation and results obtained using the new technique. The technique is interesting as it requires a nonzero noise component in the image signal being processed in order to generate a gray scale.

The aliasing problem in computer-synthesized shaded images.

Abstract: : This paper describes work toward improving the quality of computer-synthesized shaded images. Current (practical) hidden-surface algorithms produce an image whose precision is strictly limited by the number of picture elements. Problems caused by this limitation are described and explained in the text. Other image production media such as television and screen printing processes exhibit the same problems, but to a far lesser extent. Therefore, current image production media are surveyed and compared to computer-synthesized images with a view toward establishing a criterion for acceptable image quality. The problems to be seen in computer-synthesized images are predominantly caused by a phenomenon known as aliasing. Aliasing is an artifact of the process of producing an image made of discrete dots. A well known cure for aliasing is motivated and explained in the text. The notions of sampling and convolutional filtering are introduced to assist the explanation. Based on these techniques, an algorithm for computing the intensity of a single dot of an image is developed. The algorithm is applied to a test pattern which serves as a worst case for the problems caused by aliasing.

Gray scale interpolation technique

Abstract: Expanded gray scale information is recovered from quantized video input data in a raster scanned imaging system by utilizing an interpolation process to predict a gray scale value for each element of output data from the quantized levels of a m × n matrix of input data elements. The prediction matrix for each output data element includes the spatially corresponding input data element, together with vertically and horizontally input data elements.

Piecewise Approximation of Pictures: Further Experiments.

Abstract: : In an earlier report, a new method of generating skeleton representations of noisy, grayscale pictures was described. This supplemental report investigates some variations on the basic method, and also shows show approximations to the picture can be constructed, given its skeleton. (Author)