Showing papers on "Grayscale published in 1981"

On connectivity properties of grayscale pictures

Abstract: : A grayscale digital picture is called 'connected' if it has only one connected component of constant gray level that is maximal, i.e., not adjacent to any component of higher gray level. This note establishes some equivalent conditions for connectedness, and also defines a grayscale generalization of the genus in terms of sums of local property values. (Author)

A Representation for Visual Information.

Abstract: : This dissertation presents a new technique for representing digital pictures. The principal benefit of this representation is that it greatly simplifies the problem of finding the correspondence between components in the description of two pictures. This representation technique is based on a new class of reversible transforms (the Difference of Low Pass or DOLP transform). A fast algorithm for computing the DOLP transform is then presented. This algorithm, called cascade convolution with expansion is based on the auto-convolution scaling property of Gaussian functions. Techniques are then described for constructing a structural description of an image from its Sampled DOLP transform. The symbols in this description are detected by detecting local peaks and ridges in each band-pass image, and among all of the band-pass image. This description has the form of a tree of peaks, with the peaks interconnected by chains of symbols from the ridges. The tree of peaks has a structure which can be matched despite changes in size, orientation, or position of the gray scale shape that is described.

Techniques For Speckle Noise Removal

Abstract: In this paper, several techniques to reduce speckle noise (more generally signal independent multiplicative noise) in images are studied. The techniques include gray scale modification, frame averaging, low-pass filtering in the intensity and density domains, and application of the short space spectral subtraction image restoration technique in the density domain. Some discussions on the theoretical basis of the techniques studied are given and their performances are illustrated by way of examples.

Gray scale image data compression with code words a function of image history

Abstract: The present invention relates to a method and apparatus for compacting gray-scale image data which maintains extremely good picture quality and can result in typical images in a compression ratio of 5 to 1 and even better if a final step of arithmetic coding is used. The method is a special application of adaptive differential pulse code modulation (DPCM) which utilizes a prediction of smoothness surrounding a current pel to determine variable length codes to convey the quantized error. Thus, a continuously adaptive variable length code is produced which may be accurately decoded without using any further marker (code indicator) bits. For each pel and "error bit" is generated to indicate to the decoder if the predicted quantization range is adequate. These eroror bits can be further significantly compressed. This method permits the use of a "zero bit" per pel mode for the data transmission (1 "error bit" per pel actually transmitted) and provides for the automatic detection of the particular variable length compression code utilized for transmitting the quantized error (EY) for a particular pel. Utilizing the concepts of the present invention the inventors have obtained compression rates of approximately 1.5 bits per pel that produce a gray scale image at the decoding end of such a data transmission or storage system which has excellent quality (equal to 5 bit DPCM). By adding the concept of arithmetic coding to the previously set forth method, due to the nature of the statistical distribution of said special purpose error bit patterns, a compressed data set of less than 1 bit per pel has been achieved. This was produced from an original 8 bit per pel gray scale image.

Method and apparatus for forming high resolution halftone images

Abstract: Halftone images are formed from dots selected from a dot character font memory storing information representing halftone dots of different sizes and shapes corresponding to different gray scale tone values or image densities. An original image is first scanned to sample its tone values at minute intervals exceeding the desired dot resolution of the reproduction. These sample values are digitized by an A/D converter which converts them to multibit binary numbers. Adjacent samples are compared to determine the average image density in a particular area, as well as the rapidity of rate of change of image density within that area. If the rate of change of image density in a given area is below a selected threshold value, the area is designated as low detail and the multibit binary number representing the result of the average density calculation over the area is used to select a dot character from the font memory for reproducing that area of the image. If, however, the rate of change of image density exceeds the selected threshold value, indicating an area of relatively high detail, the area samples are used to select special dot shapes and positions for use in reproducing that sampled area. This technique achieves a higher resolution halftone image for a given amount of stored data than prior techniques, as well as achieving a higher "apparent" resolution to the observer.

Method and apparatus for automatic recognition of image and text/graphics areas on a master

Abstract: An apparatus and method for automatic recognition of image and text/graphics areas on a master undertake an opto-electronic scanning of the master with analog values obtained by the scanning being sampled and converted into digital information which is stored in a data field which is divided into a number of windows having edge lengths selected to be greater than the spacing between two successive lines of text. A grayscale value histogram is generated for each window and is statistically analyzed for determining whether the area of the master represented by the window is predominantly a text/graphics area or an image area based on known statistical characteristics generally related to each type of area.

Pulse width modulation greyscale system for halftone printer

Abstract: A one dimensional electronic halftone generating system having a source of digital data representative of pixel greyscale, a counter to store the digital data, and pulse producing logic responsive to the counter to activate a laser modulator in accordance with the digital data representative of each pixel. In particular, a six bit data word represents one of 64 greyscale states for a particular pixel. The pulse producing logic responds to the particular data word to produce a pulse of a given duration or width to drive the laser for a given time period. The duration of the pulse, representing one to 64 states for a given pixel, will produce a given discrete greyscale value for each pixel.

Digitized longitudinal tomography.

Abstract: An analog video longitudinal tomographic system has been converted to a digital format that reconstructs the tomographic section through the use of matrixes representing the gray scale values of the analog-recorded video images. This was done so that some simple preprocessing could be used to eliminate electronic noise and thereby increase the effective signal to noise ratio. Signal to noise was also increased by the elimination of the analog image displacement circuits (ramp generators). In addition to an improvement in the diagnostic quality (gray scale) of anatomic images, a capability to image contrast differentials as low as 1% has been achieved. A display system provides the ability to use windows having both variable central levels and widths.

Scintigraphic image contrast-enhancement techniques: global and local area histogram equalization.

Abstract: this article develops two contrast-modification techniques for the display of scintigraphic images. Based on histogram-modification techniques, histogram equalization, where each level of gray is used to the same extent, gives maximum entropy. The first technique uses the application of histogram equalization in the whole image. To eliminate contrast attenuation in image areas that represent a statistically small but important portion of the gray scale histogram, local area histogram equalization has been applied to images with differences in intensity. Both techniques were tested using a phantom with known characteristics. The global equalization technique is more suitable to bone scintigraphies, and some well-chosen boundaries improved the differnce between two comparable areas. For liver scintigraphies, where intensity is quite equal in every pixel, a local area equalization was chosen that allowed detection of heterogeneous structures. The images resulting from histogram-equalization techniques improve the readability of data, but are often far from usual images and necessitate an apprenticeship for the physician.

The GOP Parallel Image Processor

Abstract: Images contain a great deal of information which requires large processing capabilities. For that purpose fast image processors have been developed. So far they have mainly dealt with processing of binary images obtained by thresholding gray scale images. For segmentation of images having more subtle features such as noisy lines or edges, texture, color, etc. more elaborate procedures have to be used.

Conversion of an analog image signal into a binary image signal

Abstract: An image signal processing system for converting an analog image signal into a digital or binary image signal, capable of representing half-tone or gray scale when the corresponding visual image is reproduced by a dot-matrix type printer, is provided. The present system includes storing means for storing at least an array of thresholds, at least one of the thresholds being different in level from the other to form an array pattern. Such a threshold array is used as a reference level in producing a binary image signal. Half-tone is represented by the degree of black dot density per unit area.

Video Framerate, Resolution and Grayscale Tradeoffs for Undersea Telemanipulator Control

Abstract: The high costs associated with a human diver working at ocean depths greater than 100m makes the use of remotely controlled visual inspection and manipulation attractive. However, long coaxial cables from the surface to the remote teleoperator cause additional difficulties. Therefore, sound communication without a tether is desirable. This form of telemetry, however, poses severe bandwidth restrictions so that its use for image transmission is in question. The product of Frame Rate (F) in frames per second, Resolution (R) in total pixels and grayscale in bits (G) equals the transmission baud rate in bits per second. Thus for a fixed channel capacity there are tradeoffs between F, R and G in the actual sampling of the picture for a particular manual control task - in the present case remote undersea manipulation. A manipulator was used in the MASTER/SLAVE mode to study these tradeoffs. Images were systematically degreaded from 28 frames per second, 128 \times 128 pizels and 16 levels (4 bits) grayscale, with various FRG combinations constructed from a real-time digitized (charge-injection) video camera. When subjects first saw the video pictures with which they had to perform remote manipulation tasks, they refused to believe that they could suceed. Much to their surprise, however, they discovered that they were able to perform with a considerably degraded picture. It was found that frame rate, resolution and grayscale could be independently reduced without preventing the operator from accomplishing his/her task. Threshold points were found beyond which degradation would prevent any successful performance. It was observed that frame rate and grayscale could be degraded considerably more than resolution before teleoperation became impossible. Isoperformance curves (curves of constant performance) were found for two subjects for various combinations of frame rage, resolution, and grayscale. These results were found to correlate closely with isotransmission curves (curves along which the information transmission rate is the same). A general conclusion is that a well trained operator can perform familiar remote manipulator tasks with a considerably degraded picture, down to 50 K bits/ sec, well below the several m bits/sec (5 MHz) normally used for broadcsat video.

Preparation of master film from negative color film type original image

Abstract: PURPOSE:To prepare a superior printing master film directly from a negative color film original image using a conventional electronic color scanner, by compensating a specified orange color derived from an automask. CONSTITUTION:A negative color film type original image and a transparent gray scale are stuck to the original side cylinder of an electronic color scanner, and an orange color filter corresponding to an automask color is applied to the transparent gray scale. A reference value of the input side photomultiplier of the electronic color scanner is set using said scale with its orange color compensated, then the negative color film type original image is scanned to prepare each master film of cyan, magenta, and yellow, and next, triple exposures for forming said masters are applied to a photosensitive film to form a black master film.

Radiographic apparatus with logarithmic video compression

Abstract: A source of radiation irradiates an area of interest of a patient. An image intensifier receives the x-rays which have traversed the patient and provides an optical image of an x-ray shadowgraph through the examined area of the patient. A television camera converts the optical image into a video signal. A signal processor operates on the video signal by adding an offset signal to the gray scale signal and by logarithmically compressing the gray scale portion of the video signal. An automatic zero circuit is provided which readjusts the offset signal between each horizontal sweep of the television camera. The logarithmically compressed gray scale portion of the video signal and the synchronization portion are received by an image processor. The image processor digitally stores a mask image or shadowgraph of the patient before being injected with an x-ray opaque contrast agent. The image processor also stores in a post contrast image or shadowgraph of the same area of the patient after the patient has been injected with an x-ray opaque contrast agent. The image processor processor subtractively combines the mask image with the post contrast image to produce a difference image. A video monitor displays the difference image.

Video framerate, resolution and grayscale tradeoffs for undersea telemanipulator

Abstract: The product of Frame Rate (F) in frames per second, Resolution (R) in total pixels and grayscale in bits (G) equals the transmission band rate in bits per second. Thus for a fixed channel capacity there are tradeoffs between F, R and G in the actual sampling of the picture for a particular manual control task in the present case remote undersea manipulation. A manipulator was used in the MASTER/SLAVE mode to study these tradeoffs. Images were systematically degraded from 28 frames per second, 128 x 128 pixels and 16 levels (4 bits) grayscale, with various FRG combinations constructed from a real-time digitized (charge-injection) video camera. It was found that frame rate, resolution and grayscale could be independently reduced without preventing the operator from accomplishing his/her task. Threshold points were found beyond which degradation would prevent any successful performance. A general conclusion is that a well trained operator can perform familiar remote manipulator tasks with a considerably degrade picture, down to 50 K bits/ sec.

Image hard copying device

Abstract: PURPOSE:To read an image easily and accurately by measuring only the quantity of light on a gray scale, and thus photographing an image so that a hard copy which has the best desired degree of blackening is obtained. CONSTITUTION:An input video signal is converted by a video controller 4 into a video signal, and a display device 5 displays an image on a CRT5B and also display the brightness level of the screen of the 5B on a gray scale display part 5A by a gray scale. A sensor 8 detects the quantity of light on the gray scale, and a detection signal obtained by measuring only the quantity of light on the display part 5A is supplied to an integrator 9. The integrator 9 integrates the detection signal corresponding to a set integral time and the result is stored in a memory 11. Then, a shutter release signal is sent to a camera 15 in response to the output of a photographic signal to start photographing the image on the 5B. The photographic signal is supplied to a timer 12 as well and a phogography end signal is outputted to a controller 14 a certain time later, thereby supplying a shutter closure signal to the camera 15.