Picture Points Research Articles

Optimal histogram matching by monotone gray level transformation

This paper investigates the problem of optimal histogram matching using monotone gray level transformation, which always assigns all picture points of a given gray level i to another gray level T ( i ) such that if i ≥ j , then T ( i ) ≥ T ( j ). The objective is to find a transformed digital picture of a given picture such that the sum of absolute errors between the gray level histogram of the transformed picture and that of a reference picture is minimized. This is equivalent to placing k 1 linearly ordered objects of different sizes one by one into k 2 linearly ordered boxes of assorted sizes, such that the accumulated error of space underpacked or overpacked in the boxes is minimized; the placement function is monotonic, which ensures a polynomial time solution to this problem. A tree search algorithm for optimal histogram matching is presented which has time complexity O ( k 1 × k 2). If the monotone property is dropped, then the problem becomes NP -complete, even if it is restricted to k 2 = 2.

A new shape factor

A new shape factor for objects in a binary picture is presented. It is based on the average distance between an interior picture point and the nearest boundary point. Its properties are compared to the common shape factor P 2 4πA . The new shape factor is shown to be easily computable.

Image segmentation using a local extrema texture measure

An image segmentation technique is proposed which uses a texture measure that counts the number of local extrema in a window centered at each picture point. Four gray level pictures are derived, each of which represents a texture or gray level property of the original image. These intermediate pictures are used to derive the number of segments in which to divide the original image. The segmentation is then performed by assigning each pixel in the original image to a region by using a four-dimensional distance measure on the intermediate pictures, comparing each location to each selected segment. This process is then repeated in a hierarchical structure using decreasing window sizes so that smaller regions within the larger ones are defined. The computations required are amenable to real-time video implementation using state-of-the-art devices.

Switching components and the ambiguity problem in the reconstruction of pictures from their projections

The information in a digital picture may be compressed by summing gray levels over known paths, or rays, of the picture. A projection is an ordered set of ray sums. Sets of projections may be used to store pictures in compressed form. Given a projection set, reconstruction is achieved by operating on the projection set to produce either the original picture or an approximation to it (called a similar picture). The latter is due to the ambiguity of the reconstruction technique inherent in the data compression. This paper describes the ambiguity problem resulting in picture reconstruction from projection sets. The concept of switching components, a key factor in the ambiguity, is discussed. Switching components are groups of picture points which can be changed in a certain way (therefore changing the original picture to a “similar” picture) without affecting the projection set. A technique is developed that addresses itself first to unambiguous areas of the picture in reconstruction. This technique is used along with more traditional methods for the doubtful areas.

Short communication. A system for the automated diagnosis of abnormality in breast thermograms.

Thermography has been proposed as a method of screening for early breast cancers in apparently well women (Feasey et al., 1975). A rapid, automated means of diagnosing abnormality in thermograms would be less expensive than visual interpretation in a large scale screening programme (Ziskin et al., 1975; Evans et al., 1976). Towards this end, a Barr and Stroud IR11 thermography unit has been interfaced to a Varian 620L minicomputer system and software developed to analyse breast thermograms. A very simple technique for obtaining the breast outline has been devised, and criteria for abnormality are being investigated. The IR11 unit operates over a 10°C temperature range set at 25.8°C to 35.6°C; the scanner incorporates a black body reference and has a fixed focal length. An 80-line picture, each line containing 120 picture points, is input to the computer memory. Each picture point contains the calibrated temperature of a 3 × 3 mm segment of the scanned scene area.

The application of image pickup and storage‐display techniques to the high resolution electron microscope

SUMMARYThe advantages of using image‐intensifiers and other image pickup systems as an aid to the observation of the image in the electron microscope have been known for many years, and a review of a number of the systems employed so far is presented here. The additional advantages to be gained by the use of a sensitive TV pickup tube in conjunction with a storage tube are discussed, with particular reference to a proposed system for use with a high voltage, high resolution, electron microscope. It is shown that the prime limitation to the signal‐to‐noise ratio obtainable in the image pickup‐display chain is due to the noise in the electron microscope signal itself, and that with the proposed pickup and storage tube arrangement a field of 800 by 600 picture points, with adequate signal‐to‐noise ratio, should be obtainable for a current density of 10−9 A/m2 in the image plane of the microscope if an integration period of about 3 s is used.

On the use of binary and gray code schemes for continuous-tone picture representation

The paper discusses the idea of iterating the conversion of a continuous-tone picture from binary to Gray code representation. A simple recursive function is defined by means of which the value of the ith bit representing a picture point's grey level after the mth iteration is determined. The resulting rearrangement of grey levels as well as that of the bits throughout the planes is discussed next. The iteration is shown to repeat after 2″ steps, where n is the number of bit planes representing the picture. A data compression scheme is developed on the basis that prior to exact repetition, approximate repetitions take place during the iterations, and the resulting picture is almost the same as the original.

Texture descriptors using neighborhood information

A method aimed at obtaining descriptors of textural scenes is described. It is based upon the spatial relationship between grey levels at picture points neighboring one another. Neighborhoods of various sizes are used. This results in the generation of a small set of 2×2 matrices which can then be used to describe the texture.

Computer controlled picture scanning with application to labeled biological cells

High speed automatic processing of photographic images is of considerable value in the fields of medicine and biological research. Tests of routine and research nature are often time consuming because they must be done visually. The time factor often limits the capability for large scale microscopic examination of tissue specimens. One of the main obstacles to accomplishing the above is a limitation on the number of picture points which can be stored in a digital computer memory. This paper concerns an elementary method for computer examination of photographic images without the necessity for storing an entire digitized picture in computer memory (which can be impossible). The method involves using digital feedback from the optical processing equipment (flying spot scanner) to isolate the most important regions of the picture.

Ordered search techniques in template matching

Digital template matching can be made more efficient by selecting the order in which template points are compared to the corresponding picture points (for each position of the template on the picture).

A pyroelectric thermal imaging camera tube

This paper proposes the use of a thin slice of a pyroelectric single crystal as the target of an electron beam scanned camera tube. This target would be sensitive to thermal images generated by black body radiation. It is shown that 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> resolvable picture points per cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of a TGS target at a frame rate not lower than 10 Hz and a thermal resolution of 1°C in the scene should be obtainable. A pyroelectric thermal imaging camera tube based on these principles has been built and its operation will be described elsewhere [1].

Piecewise Fourier Transformation for Picture Bandwidth Compression

Recent advances in digital computer and optical technology have made image spectra determination practical. Pratt and Andrews [1] studied bandwidth compression using the Fourier transform of complete pictures. By treating pictures adaptively on a piecewise basis, picture detail is better represented. Also, subjective preferences of human vision can be used, which result in further improvements in picture quality. The original picture is sampled and then divided into small subsections. Each subsection is expanded in a two-dimensional Fourier series. The L -Fourier coefficients of largest absolute value are determined for each subsection, where L is proportional to the standard deviation of the picture samples in the subsection. The frequencies and complex amplitudes of those L -Fourier coefficients are transmitted. The number of quantization levels used for the Fourier coefficients in each subsection is made dependent on the standard deviation of the picture samples in the subsection, and the size of the quantum steps is made dependent on the magnitude of the largest Fourier coefficient of the subsection, aside from the average value. The frequencies of the coefficients correspond to positions in a twodimensional spatial frequency plane. These positions, or twodimensional frequencies, are transmitted by run-length coding. The process is adaptive in the sense that, its parameters vary from subsection to subsection of the picture in an effort to match the properties of the individual subsections. Subsection size and other important system constants are chosen with knowledge of the properties of human vision. We are able to obtain high-quality reconstructed pictures, using on the average 1.25 bits per picture point.

Directional Correlation--A Technique to Reduce Bandwidth in PCM Television Transmissions

Utilizing the new tool of frame storage of PCM encoded television pictures, a new technique for reducing the bandwidth requirements for transmission is described. The method involves the use of the high directional correlation inherent in picture point samples of the same frame, as well as frame to frame correlation. Using the procedures developed in the paper, a block diagram of a transmitter and receiver utilizing such a principle is illustrated and discussed. It is also shown how this technique improves on that of both simple and modified differential PCM encoding for television transmission.

Low-Resolution TV: Subjective Effects of Frame Repetition and Picture Replenishment

Using the experimental television facility described in a companion paper, frame repeating and point-by-point selective replenishment of picture elements have been accomplished in real time. On the basis of initial experiments, using the head-and-shoulder view of a person as the picture source, such as is likely to be encountered in a visual communication system, the following tentative conclusions have been reached: (i) The motion rendition with a 15 new pictures/second frame repeating system, while not flawless, is reasonably good. (ii) Selectively replenishing one-quarter of the picture points per frame gives a better continuity of motion but results in objectionable patterns. (iii) Picture quality greatly depends on the pattern of picture replenishment. Of the five replenishment patterns tested, two result in pictures which are significantly better than the other three. (iv) In informal viewings, opinion has been so divided that no preference has been established between simple 15 new pictures/second frame repeating and the more satisfying schemes for picture replenishment. (v) The frame repeating and replenishment systems produce gross impairment during zooming and panning; consequently, these systems in their present form are unlikely to be useful for broadcast television. The impairments observed in these systems are subjective and not yet predictable. This emphasizes the importance of subjective testing of systems in real time.

Errors in Absolute Orientation (I)

Model deformation or displacement of picture points after absolute orientation is discussed as a fuction of observational error of photographic co-ordinates. As a simple example, the case of a mathematical grid plate is analysed by six point method with numerical discussions for two cases of observation : mono-ocular co-ordinate comparator method and stereo-comparator method. Further the author gives the influence of the error of geodetic co-ordinates of control points upon the displacement of model co-ordinates and an idea in selecting control points in accordance with the requirements for the accuracy of picture points in consideration.

Automatic picture detail detection in the presence of random noise

This paper is intended to be a companion to the paper in this issue by Cherry, et al., entitled "An Experimental Study of the Possible Bandwidth Compression of Visual Image Signals." It concerns particularly that part of the visual signal compression process carried out by the "picture detail detector." The purpose of this detector is to make a continuous running examination of a scanned video signal, in real time and to make successive decisions concerning the location of essential sample points. These points are the boundaries between successive step functions which adequately represent a reduced form of the picture suitable for encoding in a compression scheme. "Suitable here means an adequate representation of the picture as judged by eye. The device is based upon a statistical inference process which effectively leads to discrimination between the video signal and the background random noise based upon the fact that the statistical properties of successive picture points are different for the picture itself and for the noise.

Classification in the Food Brokerage Field

To the food broker with a retail merchandising force, the outstanding single fact which affects his day-to-day operation is the following: that an increasingly larger percentage of retail food sales passes through the hands of fewer, and very much larger, retail outlets. And nothing in the current picture points to the possibility of a reversal of this trend. Neither the growing prevalence of mergers in the field, the thorny problem of trading stamps, nor the ever present problem of markups and profits has so significant a bearing on the retail operations of the food broker as the fact first cited. With the retail food business thus undergoing dynamic and rapid change, it is essential for a food brokerage firm to take stock from time to time of the final outlets through which the products it represents move directly from store shelves to pantry shelves in order to maintain proper retail coverage. Our own retail service currently accounts for a full third of our total expense. It is the service which is most directly responsible, together with the promotional and advertising programs of our principals, for moving our brands into consumer hands. Retail sales costs continue to increase, and show no sign of taking a downward turn. It should be a matter of concern to make this increased expense at least commensurately

Über das Hauptproblem bei konvexen Rotationskörpern

It is shown that over the distance 0≤X≤8/π2 in the diagram, there is a region which is free from picture points («Bildpunkten») of the convex rotation bodies. This assertion is based on two different groupings of the convex rotation bodies into troops, namely at constant lengthl and constant radius of the equatorr, and at constantl and constant length of the resulting meridial curveL. From this, new relations like between the measurements of the convex rotation bodies follow.

Point Four and Mineral Raw Materials

VER since January 20, 1949, when President Truman proposed his Point Four-a bold new program for making the benefits of our scientific advances and industrial progress available for the improvement and growth of underdeveloped areas-there has been considerable discussion of its merits, its feasibility, and its implications. The modest beginning to a Point Four program which has recently been made has not put an end to the controversy. It is timely, therefore, to point out an important aspect of the Point Four concept which has generally been overlooked: its significance as a possible* factor in the future course of United States investment in foreign mineral production, in the light of the strategic mineral position of this country. It is true that the recent report of the International Development Advisory Board' emphasizes the need of aiding private investment in raw material production to assure the free world and its principal arsenal, the United States, of the necessary supply of those materials in the effort to maintain that freedom. Nevertheless, emphasis is on immediate or short range needs, whereas the argument to be developed in this discussion stresses a problem which would confront us even if the current threat of totalitarianism were to disappear. Under the ideological stresses of the cold war it is tempting to picture Point Four as a completely altruistic proposal which demonstrates to the world the unselfishness of this country in its concern for the well-being of mankind. A realistic appraisal of the program, however, recognizes that it is, like the European Recovery Program, an act of enlightened self-interest. A world which enjoys a higher standard of living will have greater political stability, will possess a greater purchasing power to spend on this country's exports, and, most important for the present discussion, will increase the world's available supply of raw materials through an increase in productive efficiency and the availability of capital.2 In the Russian point of view the self-interest of this country inherent in Point Four is so exaggerated as to make the program nothing more than a form of disguised imperialism. It is possible, however, to discuss the self-interest aspect of Point Four in terms of a quid pro quo without implying that this country seeks to gain any unjust advantage through the imposition of onerous terms on a beneficiary. The following discussion seeks to demonstrate that in the field of mineral raw materials the self-interest of the United States lies in an expansion of the world supply of those minerals in which this country is or will be deficient; that in the absence of Point Four assistance in this field there may be an insufficient expansion or none at all.

Multi-Channel Television

ONE of the difficulties met in designing a new system of television is the narrowness of the frequency band of the waves permissible when only one channel of transmission is used. At the Institution of Electrical Engineers on Jan. 6, C. O. Browne showed how this difficulty can be largely overcome by using a number of transmission channels. By using five channels, the frequency band is increased five times and the difficulties of design are greatly diminished. In addition, the velocity with which the scanning spots travel over the surface of the picture is decreased and the difficulties of good synchronisation are largely obviated. To get a moderately good picture, experience shows that the picture should consist of 15,000 picture points at least, and the picture must be scanned about 12½ times per second. This number was chosen because the standard frequency of the supply mains in Great Britain is 50. With small screens, satisfactory results are obtained, but when a ground glass screen measuring 24 in. x 16 in. is used there is a decrease in the brilliance of the received image. With the large received picture, the effect of flicker is pronounced and a higher scanning speed than 12½ pictures per second needs to be used. The author has investigated the best conditions for operating the Kerr cells used in the receiver, and discusses the effects produced by geometric, nonlinear, and frequency distortion.