Showing papers on "Pixel published in 1978"

A hidden-surface algorithm with anti-aliasing

Abstract: In recent years we have gained understanding about aliasing in computer generated pictures and about methods for reducing the symptoms of aliasing. The chief symptoms are staircasing along edges and objects that pop on and off in time. The method for reducing these symptoms is to filter the image before sampling at the display resolution. One filter that is easy to understand and that works quite effectively is equivalent to integrating the visible intensities over the area that the pixel covers. There have been several implementations of this method - mostly unpublished - however most algorithms break down when the data for the pixel is complicated. Unfortunately, as the quality of displays and the complexity of pictures increase, the small errors that can occur in a single pixel become quite noticeable. A correct solution for this filter requires a hidden-surface algorithm at each pixel! If the data at the pixel is presented as a depth-ordered list of polygons then the average visible intensity can be found using a polygon clipper in a way similar to that employed by two known hidden-surface algorithms. All of the polygons in a pixel are clipped against some front unclipped edge into two lists of polygons. The algorithm is recursively entered with each new list and halts when the front polygon is clipped on all sides, thereby obscuring the polygons behind. The area weighted colors are then returned as the value to be added to the other pieces in the pixel.

Automatic multimode continuous halftone line copy reproduction

Abstract: An image data handling system to automatically detect and segregate from a stream of image pixels high frequency half-tone image input, continuous tone image input, low frequency half-tone image input, and line image input which may be present in the pixel stream. The image pixels are first autocorrelated in accordance with a predetermined algorithm to detect if high frequency half-tone image data is present. Data of this type found is processed by first descreening and then rescreening at a lower frequency to provide binary level pixels. The pixel stream is analyzed for the presence of continuous tone image data. Where found, such data is processed by a template screening process to provide binary level pixels. Remaining pixels comprising low frequency half-tone and line copy image data are thresholded to provide binary level pixels.

Progressive image transmission

Abstract: A gray-scale image is progressively transmitted over a narrow-band channel after the gray-scale values of all picture elements (pixels) have been formatted into a hierarchical structure of picture subdivisions of successive sizes from entire image down to basic element values. Each formatted value is encoded as an approximate average of paired values. Transmission involves sending the primary value, representing the overall gray-scale magnitude, and following with successively split image values so that the entire image can be reconstructed at a receiver in progressively finer detail until the ultimate image results. The coding is nonredundant and full reconstruction is accomplished by transmitting the same number of bits that are required to send the image pixel-by-pixel and line-by-line with the difference that an intermediate version can supply enough image detail for recognition. Unwanted images can be aborted at any intermediate stage, thus saving overall transmission time and effecting an equivalent picture compression when many images need to be examined in rapid succession.

System for expanding the video contrast of an image

Abstract: A system, and method, is disclosed for substantially increasing the dynamic range of contrast of an input sequence of pixels representative of an image. In a preferred embodiment a first circuit is responsive to an input sequence of pixels representative of an image for developing bias and gain parameters. These bias and gain parameters are respectively utilized by first and second function generators to generate bias correction signals and gain correction signals, respectively. A delay circuit delays the input sequence of pixels to synchronize said input sequence with the bias correction signals and the gain correction signals. A first expansion circuit expands in a first direction the range of contrast of the delayed input sequence of pixels as a function of the bias correction signals to produce a first contrast expanded sequence of pixels. A second expansion circuit expands in a second direction the range of contrast of the first contrast expanded sequence of pixels as a function of the gain correction signals to produce an output sequence of pixels which has a substantially expanded dynamic range of contrast in relation to the dynamic range of contrast of the input sequence of pixels.

Image interpolation system

Abstract: Analog image data pixels are sampled and held to produce a box car wave representative of the image data. Wave height differences are bridged by linear interpolation, with frequency enhancement imposed at the bridge junctures. The modified image wave is thresholded and sampled at a multiple of the original frequency to provide an image pixel stream comprised of both original image pixels having one or more interpolated image pixels therebetween. One or more intermediate image lines are interpolated by comparing binary image data, portions of which may be interpolated, on a pixel by pixel or multiple pixel basis one line pair at a time. The pixel comparison produces an address used to identify a specific image pixel pattern from multiple image pixel patterns stored in memory. The image pixel pattern taken from memory is used to form the interpolated intermediate line or lines.

High resolution input scanner using a two dimensional detector array

Abstract: In an input scanner the subject to be scanned is translated in a cross scan direction relative to a two dimensional, integrated CCD detector array or the like so that successive full scan length segments of the subject are sequentially imaged onto the array. The photosensitive zones of the detectors within the different rows of the array are laterally staggered so that each of the detectors responds to a specific spatially predetermined resolution element or pixel of each scan line. The detectors generate data samples in response to those pixels, but the data samples representing adjacent pixels of any given scan line are distributed over multiple rows of the array in accordance with a two dimensional distribution function which depends on the staggering of the photosensitive zones of the detectors. If multiple scan lines are simultaneously imaged onto the array, buffered destaggering electronics, operating in accordance with the inverse of that distribution function may be utilized to arrange the data samples representing adjacent pixels in a serial video data stream having a conventional raster scan format. If, however, only one scan line is imaged onto the array per imaging frame, the data samples may be directly read out of the detectors in a scan line-by-scan line serial video data stream.

Texture Characterization and Texture-Based Image Partitioning Using Two-Dimensional Linear Estimation Techniques

Abstract: A new approach to texture characterization and texture-based image partitioning is presented. In this approach the gray level of each pixel of an image is estimated from a weighted sum of gray levels of its neighbor pixels. The weight coefficients are determined so that the mean square estimation error is minimized. The obtained two-dimensional estimator characterizes the texture of the sample and can be used to discriminate other classes of textures. This texture characterization technique is applied to image partitioning, and two partitioning procedures are developed. Experimental results obtained by their application are also shown.

Design of a Local Parallel Pattern Processor for Image Processing

Abstract: This chapter presents an approach called microprogrammable local parallel pattern processor (PPP) which has several basic image processing functions in a simple hardware. It discusses major concepts considered for the design of the PPP. The chapter describes the details of the implementation of the basic image processing functions. It shows some simple examples of programming the PPP. By using dynamically rewritable microprogram architecture, powerful and flexible programs of image processing were designed and demonstrated in the interactive image processing system. Two-dimensional linear coordinate transformation (affine transformation) is performed by the address control module. The PPP includes seven special purpose modules for two-dimensional convolution, point mapping, linear coordinate transformation, logical filtering, histogram generation, region labeling, and pixel operations. These functions can be combined for more global and complex functions such as texture analysis, shape identification, region separation, and so on. The scratch-pad memory is used for histogram counting registers for image data.

Device for delineating zones in a video image display

Abstract: Data derived from multiple x-ray views of a body layer is processed in accordance with an image reconstruction algorithm by a central processing unit (CPU) to result in a matrix of digital data corresponding with picture elements (pixels) which are for being displayed on a tv or video monitor. A device for delineating or identifying a region in the displayed picture with a box, irregular trace, or cursor with a bright dotted line uses a trackball to generate data signals corresponding in position with pixels in the matrix. The trackball generated data is processed for producing video picture modulating signals corresponding with the pixels in the matrix to which they positionally relate. The modulating signals are overlayed on the composite video signals from the display controller with a video mixer.

Pseudogaussian video output processing for digital display

Abstract: A method and apparatus for generating a pseudogaussian characteristic in the display of video information presented in digital form from a read-write memory that is continuously updated as the scan input requires, and read out one line at a time, preferably with conventional TV fields of odd and even interlaced lines. Picture elements (pixels) of each line L read for display are summed with a predetermined fraction of the sum of the values of corresponding pixels of adjacent lines L-1 and L+1, thus forming a vertical pseudogaussian calculation for the pixels of line L. Horizontal pseudogaussian calculation of the pixels is then performed in a similar manner using two pixel delay elements connected in cascade and connected to an adder to presum values of pixels P-1 and and P+1 as an input to a second adder which sums the output of the first adder, divided by a predetermined value, with the value of pixel P.

Digital scan converter with programmable transfer function

Abstract: A digital scan converter is provided with a programmable transfer function for video display of picture elements (pixels) using a main random access memory for storing a pixel array to be read out periodically for display, and to be selectively read out while scanning for updating with a value derived from an auxiliary random access memory addressed by the composite of an old pixel value to be updated and the new pixel value Each memory location of the auxiliary memory stores a value derived from a table defining the transfer function desired for the entire range of new and old pixel values An alternate transfer function is stored in a second block of the memory and selectively called out by a prefix set to a 1 or 0 in the most significant bit position of the composite address word

Subpixel X-Y coordinate encoding

Abstract: A technique of encoding digitized video input signals to an arrayed display memory in a manner to maximize the probability of entering the best picture element (pixel) value into a particular X,Y location by effectively dividing a pixel area into an array of subpixels, and weighting the value of pixel as a function of the position of a display vector through the subpixel array. First the location of a vector to be displayed in an X-Y coordinate system is determined, and then with respect to the subpixel array of each pixel, it is determined whether the vector traverses a core or central area, an edge or a corner. For these respective vector locations, the pixel value is weighted, for example, 100%, 50% and 0%.

Digital scene storage

Abstract: A scene which is divided into a plurality of pixels is raster scanned. During each scan an analog signal derived from a binary number and representing a given light intensity is compared against other analog signals representing the light intensity of each of the pixels. At any time when the light intensity of a pixel is greater than the given light intensity, the binary number associated with that given light intensity is stored in a register of a multiregister memory whose registers are assigned to the respective pixels. After each scan the given light intensity is increased.

Digital Image Processing by Use of Local Statistics.

Abstract: : Computational techniques involving contrast enhancement and noise filtering on two-dimensional image arrays were developed, based on their local mean and variance. These algorithms are nonrecursive and do not require a transform. They share the same characteristics in that each pixel is processed independently. Consequently, this approach has an obvious advantage when used in real-time digital image processing applications and where parallel processors can be used. For both the additive and multiplicative cases, the a priori mean and variance of each pixel is derived from its local mean and variance. Then, the minimum mean-square-error estimator in its simplest form is applied to obtain the noise-filtering algorithms. For multiplicative noise a statistical optimal linear approximation is made. Experimental results show that such an assumption yields a very effective filtering algorithm. Examples on images containing 256 x 256 pixels are given. Results show that in most cases the techniques developed in this report are readily adaptable to real-time image processing. (Author)

Digital Color Image Compression In A Perceptual Space

Abstract: A nonlinear mathematical model for the human visual system (HVS) is selected as a preprocessing stage for monochrome and color digital image compression. Rate distortion curves and derived power spectra are used to develop coding algorithms in the preprocessed "perceptual space." Black and white image compressions down to .1 bit per pixel are obtained. In addition, color images are compressed to 1 bit per pixel (1/3 bit per pixel per color) with less than 1% mean square error and no visible degradations. Minor distor-tions are incurred with compressions down to 1/4 bit per pixel (1/12 bit per pixel per color). Thus, it appears that the perceptual power spectrum coding technique "puts' the noise where one can not see it. The result is bit rates up to an order of magnitude lower than those previously obtained with comparable quality.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Analog video convolver for real time two-dimensional image processing

Abstract: In a convolver, analog video waveforms for each horizontal line to a raster scanned video monitor are sampled at regular intervals with a high speed shift register such as a charge coupled device to obtain trains of picture elements (pixels) which are transferred line-after-line to a series of registers to thereby delay the lines by the number of register stages used. As the trains are transferred the pixels are simultaneously supplied to delay elements to delay corresponding pixels in each line by a given amount in reference to the individual pixel which is to be convolved at the instant. The delayed pixel signals existing at the instant are variously processed in summing devices and the result is used to act on the individual pixel to convolve it in accordance with the filter function which is desired.

A device structure and spatial spectrum for checker-pattern CCD color camera

Abstract: In order to develop practical color cameras with useful resolution, a novel image processing and charge-coupled device (CCD) structure is proposed which results in shrinking chip size and easing photolithography The resolution of CCD cameras is limited by the aliasing errors associated with spatially discrete sampling on a photosensing area The photosensing array arranged in a two-dimensional face-centered rectangular lattice scheme, and the spatial offsetting technique among three CCD's avoid undesirable signal carriers accompanied by aliasing errors A unique signal processing about vertical correlation of an image is put to use, in order to reduce spurious effects of aliasing These image processing techniques are theoretically treated on a spectrum space The photosensing array arranged in a face-centered rectangular lattice scheme is successfully implemented with a zigzag-transfer CCD with checker-pattern sensing sites, which relax some of the lithography requirements and improve image qualities By means of the zigzag-transfer CCD structure and the image processing, the resolution of color camera has been expanded by a factor of 25, compared with that of the conventional CCD cameras employing the same number of pixels According to the theory, the factor may be increased further up to three or four

Ship detection from landsat imagery

Abstract: Recent inspection of Landsat CCT printouts revealed that the detection of ships is possible. Experience has shown that MSS band 7, because of low radiance values from water and the resultant high S/N ratio, is the best MSS band for a "quick look" inspection of CCT printouts for possible ships. Following verification of the target on CCT printouts of other MMS bands the ship's size, orientation, state of motion, and direction of movement can be determined from the total number of pixels occupied by the target for each MSS band, the orientation of these pixels, and the target's maximum and total pixel radiance values. This paper presents the procedures used for detecting ships, and discusses the problems and limitations of the overall technique as related to ship parameters, sea state and turbidity, pixel overlap, relative geometric fidelity between pixels, and solar elevation angle. /Author/

A multiple output CCD imager for image processing applications

Abstract: A 324 × 340 pixel silicon charge coupled area imager has been developed which uses non-destructive floating gate readout techniques and on-chip delay lines to provide nine simultaneous video output signals. These signals represent a 3 × 3 block of image data which scans the array as the device is read out. The 3 × 3 block can be used to implement various neighborhood operators in the analog domain for real-time image processing applications, such as edge detect ion and enhancement and star image centroid determination. The device is fabricated using a three-phase, three-level polysilicon buried channel process. Chip size is 1.27 × 1.27 cm and pixel size is 25 × 25 micrometers.

Synthesizing method of stereo images from plural sheets of tomographic images

Abstract: PURPOSE:To enable stereo construction to be expressed with one sheet of image by converging plural sheets of tomographic images to digital information of picture element units, superposing these and giving variable densities according to the perspective from the point of view to the object existing portion of the images of the respective sectional planes. CONSTITUTION:The sections 2a, 2b, 2c... of an object 1 such as of, e.g., the heart, etc. are converted to digital information of picture element units while the tomograph obtained through reflection of ultrasonic pulses is being scanned. This digital information is inputted to an information processing unit. Here, the processing of converting the information for each picture element to binary coded information of 1 or 0, superposing these, if necessary, by turning the coordinates of the binary coded image information at specified angles, giving the lightest density to the image of the sectional plane A closest to the point of view and subsequently increasing the densities as the sectional planes go further from the point of view, is accomplished. These plotting work, judgement, etc. are all executed by a computer and the results thereof are displayed in a Braun tube or the like.

A Device Structure and Spatial Spectrum for Checker-Pattern CCD Color Camera

Abstract: In order to develop practical color cameras with useful resolution, a novel image processing and charge-coupled device (CCD) structure is proposed which results in shrinking chip size and easing photolithography. The resolution of CCD cameras is limited by the aliasilrng errors associated with spatially discrete sampling on a photosensing area. The photosensing array arranged in a two-dimensional face-centered rectangular lattice scheme, and the spatial offsetting technique among three CCD's avoid undesirable signal carriers accompanied by aliasing errors. A unique signal processing about vertical correlation of an image is put to use, in order to reduce spurious effects of aliasing. These image processing techniques are theoretically treated on a spectrum space. The photosensing array arranged in a face-centered rectangular lattice scheme is successfully implemented with a zigzag-transfer CCD with checker-pattern sensing sites, which relax some of the lithography requirements and improve image qualities. By means of the zigzag-transfer CCD structure and the image processing, the resolution of color camera has been expanded by a factor of 2.5, compared with that of the conventional CCD cameras employing the same number of pixels. According to the theory, the factor may be increased further up to three or four.

A High Resolution Solid State Charge Coupled Device (CCD) Space Borne Earth Imager

Abstract: A solid state (Charge Coupled Device) imaging system is described which satisfies the requirement for multispectral, high resolution, real time imagery. The system, using an earth resources survey satellite as its platform is configured to yield a 10 meter ground resolution with a 50 kilometer swath width at approximately 1000 km altitude. Four spectral bands ranging from 0.5 to 1.1 μm have been selected and are implemented by optically butting three 1728 pixel linear arrays (5184 pixel per band) on appropriate beam splitting prisms. The device employed, the Fairchild CCD 121H, shown in Figure 1, is a monolithic self-scanned image sensor utilizing two phase, buried n-channel CCD technology. The device has an element-to-element pitch of 13 μm (approximately 2000 pixel inch) and has been demonstrated to have a wide dynamic range (2500:1), Figure 2, low noise equivalent exposure and dimensionally precise photosite spacing. Consideration of focal plane design, geometric accuracy, image registration, temperature control, optical design, and noise figures are discussed. Particular emphasis has been placed on the unique properties of CCD detectors which allow for specialized post processing of the video for dealing with low contract scenarios. The paper concludes with new trends in specialized time delay and integration (TDI) mode imaging systems now under study and development at Fairchild.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Segmentation using spatial context and feature space cluster labels

Abstract: : The focus of this paper is on image segmentation processes, collectively referred to as a 'low-level' vision system. The programs which will be discussed here transform a large spatial array of pixels (picture elements) into a more compact representation through the exploitation of visual features, e.g., intensity, color, texture, etc. The goal is to detect a relative feature invariance across an area of the image and then to label all the pixels in any such area as belonging to the same region. Regions can be detected through global analyses (e.g., histogram clustering) which find interesting areas by ignoring the local textural configurations of the data, in conjunction with local anlayses (e.g., relaxation) which act as a fine-tuning mechanisms both to resolve global ambiguities and to accurately delimit region boundaries. (Author)

An Image Coding Algorithm Using Spline Functions

Abstract: This paper presents an image coding algorithm using spline functions that is competitive with the more conventional orthogonal transform methods at data rates of 1 bit/pixel or less. Spline coding has the added attraction of an optical implementation arising from the fact that least squares image approximations also produces least squares approximations to the image derivatives. A first order spline is used to approximate the proper order derivative of the image whose order is determined by an analysis presented in the paper. The image derivative is then encoded and transmitted to the user who reconstructs the image by a k-1 order integration which can be done optically.© (1978) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Forests and Pyramids: Using Image Hierarchies to Understand Landsat Images

Abstract: Computer-based Landsat image interpretation has neglected the spatial organization of the image in favour of the spectral and temporal organization. A brief survey of techniques that exploit spatial information, including multistage sampling, is given. Semantically-guided region-merging methods have been used successfully but they require sophisticated and expensive list processing facilities. Similar semantic and spatial sensitivity can be introduced by exploiting a pyramidal, hierarchical representation of the image advocated by Kelly, Tanimoto and Levine. The image pyramid is constructed bottom-up with the original image as the base. Each level is a reduced resolution version of the level below, constructed by averaging the signatures of adjacent pixels at the lower level. By classifying pixels at the higher levels one is efficiently classifying semantically uniform regions in the original image. If, however, a region''s signature lies in the spectral overlap of two or more classes its subregions will have to be considered for classification. Several refinements of this technique, including the use of semantically-based region splitting and merging techniques at each level of the pyramid, are described. .br These techniques are used to classify forest cover types on Vancouver Island in a Landsat image. The results of several initial experiments indicate that, compared to a baseline of a traditional supervised maximum-likelihood classifier, the cost of maintaining the pyramid is balanced by the vast reduction in the number of pixel classifications. The spatial homogeneity or readability of the segmented image, as measured by the number of regions, is improved by a factor of three while the accuracy of the classification is unaffected or slightly improved. When the region splitting and merging techniques are applied at each level of the imaqe pyramid the accuracy and the readability of the final segmentation both increase markedly. It is thereby demonstrated that these pyramidal techniques offer many of the advantages of the semantically-driven region-merging approach in a more flexible and efficient fashion. Indeed the two approaches have been combined to achieve substantial benefits for Landsat image interpretation.

Image quality improving method of recording picture images

Abstract: PURPOSE:To readily record good quality picture images wherein jitter, etc. are subdued by making the diameters of the picture elements forming picture image larger than the pitches of the picture images and letting the density distribution of each picture element become largest near central part.

Electronic zooming system

Abstract: PURPOSE:To secure a similar zooming of the ordinary image into an optional size by carrying out a fixed interpolative operation to reduce the geometric distortion when the picture element is reduced and obtaining the output picture element.

Picture image transmitting system

Abstract: PURPOSE:To enable a confirmation of the outline of a picture image before completion of the picture image transmission by transmitting sequentially the picture element signal groups which are extracted every one or several picture elements and then interpolating the picture image to be formed.

Effect of pixel dimensions on SAR picture quality

Abstract: In an SAR mapping system, the product of looks per pixel and number of pixels in the scene is kept constant Assuming that the returns from all resolution cells obey Rayleigh statistics, the expression for pixel SNR incorporating both speckle and additive white Gaussian noise was derived It is shown that it is possible to use fine resolution and leave the large-area estimate slightly but not much worse than if a larger pixel size had been initially decided upon