Contains reports on five research projects.Associated Press (Grant)Taylor Publishing Company (Grant)Providence Gravure, Inc. (Grant

Schreiber, William F.

Troxel, Donald E.

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Cognitive Information Processing23. Cognitive Information ProcessingAcademic and Research StaffProf. W.F. Schreiber, Prof. D.E. Troxel, Dr. C.W. Lynn,C. Konrad, M. Mcllrath, K.P. WacksGraduate StudentsR.P. Bishop, R.R. Buckley, G.J. Bunza, Y-M. Chao,R.S. Damon, A. Garcia, B. Hofman, P-Q. Hoang, M. Isnardi,M.M.A. Khan, E.A. Lee, D.S. Levinstone, J. Lofton, E. Peynard,L. Picard, J. Sara, J-P. Schott, G. Vachon, R. Velez, R. Walker23.1 Picture CodingDonald E. Troxel, William F. Schreibera. Sampling and ReconstructionMost present-day picture coding is digital; virtually all input and output images are analog. Thusthe conversion from one form to the other is everpresent and important to the quality and efficiency ofthe overall process. To elucidate the phenomena involved, a systematic study was carried out of awide variety of presampling and interpolation filters. It was found that, as suspected, the "ideal"low-pass filter was far from best, subjectively, since the least-rms-error criterion is invalid for humanobservers. Aliasing resulting from "violation" of the sampling theorem is visually traded off againstsharpness and visibility of the sampling structure which occurs with other filters. Several filtersstudied performed substantially better than the ILPF. The best combination of performance andcomputational simplicity was found in the "sharpened Gaussian" filter, which has an impulseresponse not unlike that of human vision.1b. Differential Pulse Code ModulationThis most common of image data compression systems has been widely studied. Its performancedepends in marked degree on the characteristics of the signal source, since the presence of verysharp transitions requires an unfavorable trade-off between slope overload and the granular noisewhich occurs in blank areas. Nevertheless, when this factor is carefully taken into account, we havegotten good results with a form of DPCM in which the companding characteristic is adaptivelyadjusted to local image properties. In speech coding effective adaptation is possible based only onthe coded signal. Because of the isotropic character of vision and images, this is not possible - extradata must be transmitted. Even including this extra data, we have obtained nearly "original" quality at2.2 bits/pel, nonstatistical, and 1.5 bits/pel statistical.2RLE P.R. No. 124154Cognitive Information Processingc. Two-Channel Coding SystemFor a number of years we have studied a picture transmission system in which the signal is dividedinto two channels, a two-dimensional low-pass signal ("lows") which is coarsely sampled and finelyquantized, plus the remainder ("highs") which is finely sampled and coarsely quantized with the aidof a tapered randomized quanitizer.3 While this can be thought of as a crude form of transformcoding, the two- or three-channel approach permits tailoring the separate channel coding parametersto well-known human visual properties. While the performance of the non-adaptive version of thissystem is not as good as the adaptive DPCM system mentioned above, it does feature rather simpleimplementation and excellent (PCM-like) performance in the presence of channel errors. Under agrant from the Sony Corporation, a real-time hardware system was implemented.4d. Adaptive Two-Channel Color Coding SystemThe above-mentioned system can be substantially improved by adapting the highs quantization tothe local signal properties. Blank-area signal-to-noise ratio of 50 db at about 3 bits/pel is possible inmost cases. The system is extended to color coding by transmitting a three-color lows signal plus anadaptively-companded achromatic highs signal. The color lows signal is further compressed bymapping to a perceptually uniform color space, akin to the Munsell system of subjective colornotation. Excellent quality full color images are possible at four bits/pel, compared with 24 for theuncoded signal. Further compression is possible by statistical (entropy) coding of the two-channelcoder output.5e. Randomized DPCMWe have also studied the application of pseudorandom (PRN) noise to the DPCM quantizer. Unlikeprevious efforts to apply PRN to DPCM we chose to apply the noise directly to the quantizer inside thefeedback loop. The application of PRN greatly reduces the most prominent artifacts of DPCM andallows greater freedom in the choice on the nonlinear quantizer so that slope overload can bereduced.6References1. J.N. Ratzel, Ph.D. Thesis, Department of Electrical Engineering and Computer Science, M.I.T.,1980.2. A. Zaremowitch, M.S. Thesis, Department of Electrical Engineering and Computer Science, M.I.T.,1981.3. D.E. Troxel et al., "Bandwidth Compression of High Quality Images," presented at the InternationalConference on Communication, 31.9.1-31.9.5, June 1980.4. D.E. Troxel et al., "A Two-Channel Picture Coding System: I - Real Time Implementation," IEEETrans. on Comm., COM-29, 12, 1841-1848, December 1981.5. W.F. Schreiber and R.R. Buckley, "A Two-Channel Picture Coding System: II - AdaptiveCompanding and Color Coding," IEEE Trans. on Comm., COM-29, 12, 1849-1858, December1981.RLE P.R. No. 124155Cognitive Information Processing6. D.E. Troxel, "Application of Pseudorandom Noise to DPCM," IEEE Trans. on Comm., COM-29, 12,1763-176', December 1981.23.2 Digital Wirephoto 19 SystemAssociated Press (Grant)Donald Troxel., William F. SchreiberIn previous reports, we have discussed the system we developed for the Associated Press fortransmitting pictures to newspapers. This comprises cost-effective Laserphoto* facsimiletransmitters and receivers and a computer-based image processing system (Electronic Darkroom)which permits automatic transmission and reception of pictures over many different channels,conversion between different Wirephoto scanning standards, and simultaneous editing (enlargement,reduction, cropping, combining, filtering, tone scale transformation, caption writing, etc.) of storedimages. In this last year of the project, we have continued to improve the system reliability andperformance. The major project has been the development of a device which automaticallyoverprints the computer file name onto facsimile pictures as they are simultaneously received by thecomputer and a local facsimile receiver. This greatly reduces the load on the computer system byeliminating the need to automatically retransmit ID or identification copies to enable the photographiceditors to easily associate pictures with their computer file names.23.3 Graphic Arts ApplicationsWilliam F. Schreiber, Donald E. TroxelThe vast majority of pictures produced every day are made on printing presses. The printingindustry is one of the largest in the country - five times as large as radio and TV broadcasting, andthree times as large as the semiconductor industry. This industry is undergoing a true revolution intechnology based on electronics and computers. For this and other reasons, our activities in recentyears have been focussed on understanding and improving the complicated chain of processes usedto translate images of natural scenes, or man-made graphics, into printed pages. This orientationaffects our activities in a number of ways:1. Our sponsors generally plan to use the products of our research and development in dailyproduction. Thus, the systems must be practical, reliable, and cost-effective.2. Graphic arts images are of very high quality compared to those usually used by computer image1 9 Trademark of the A.P.RLE P.R. No. 124156Cognitive Information Processingprocessors. This requires careful attention to certain factors, such as tone reproduction, not alwaysconsidered of great importance. High quality also implies very large amounts of data to be processed.3. The images we deal with are intended for human viewing, and the systems we design are alwaysoperated by people. Human perceptual and operational capabilities are central to our work.The principal operations which must be performed are the scanning and editing of individual pagecomponents, the selection and arrangement of elements on the page (composition, often erroneouslycalled pagination), the arrangement of pages on the sheet (imposition), and the control of machineswhich make printing plates for letterpress, offset, and gravure printing.We have undertaken two sizeable projects in this field with the main purpose of reducing the timeand cost of preparation of printing surfaces by means of computer control of the process. Pageelements are scanned by a high resolution laser scanner, digitized, and temporarily stored. Pages areassembled and displayed on a TV screen, the quality enhanced and editorial corrections made. Theinformation is then efficiently coded (differently for text and pictures), stored, and finally output for thepurpose of plate making.23.4 Graphics Processing for Yearbook ProductionTaylor Publishing Company (Grant)Donald E. Troxel, William F. SchreiberThis is the image processing portion of a complete system for producing printing plates foryearbooks and similar publications which use a very large number of pictures. Compared toconventional techniques, the new system is to feature lower cost, higher speed, and no reduction inquality. The work done at MIT consists of the design of a scanner station and its operating system.Physically, the station, which itself is a satellite of the Taylor Publishing Company's publishing system,comprises a small computer with associated peripherals. These include a picture display, full-framememory, disk memory, tablet and Autokon scanner. The operating system permits the stationoperator, sitting in front of the computer console, to perform, interactively, the following operations:1. Receive layout instructions for each page, from the central system, including location and sizeof graphical elements.2. Scan pictures into the system using parameters derived from the layout information.3. View scanned pictures on the display and perform aesthetic corrections, if required. View entirepage on display to verify layout.RLE P.R. No. 124157Cognitive Information Processing4. Organize graphical data in local memory as required by page layout and initiate data transfer tothe central system.The novel features of this system revolve around the use of a small computer, in combination with agraphic arts quality laser scanner and some special-purpose digital hardware, to permit input andgraphic elements, aesthetic corrections, and the organization of data for each page according tolayout information, all on an interactive basis, and in a cost-effective manner.23.5 Automated Engraving of Gravure PrintingProvidence Gravure, Inc. (Grant)William F. Schreiber, Donald E. TroxelGravure printing is characterized by high platemaking costs but inexpensive and very stableoperation of the printing press. Thus it is suited primarily to long runs, particularly of color work, ofboth high and low quality. Substantial economic benefit would accrue from reducing the cost andtime required to prepare printing cylinders, perhaps even making it practical to extend gravureprinting to certain very significant applications such as daily newspapers.In the system under development, all photographic steps between the original copy and thecylinder are eliminated by scanning into a computer system. Pictures are interactively edited, andthen all components for each page are assembled into a single disk file. Cylinders are engraveddirectly from computer storage. (In other forms of printing, four color separation films would be madefor each page instead.) Imposition and correction for ink and paper are performed in "real" timesimultaneously with engraving.The differences between this system and other existing prepress systems include substantiallyreduced storage requirements due to data compression, high cost-effectiveness, the elimination ofthe need for the operators to have long experience in color printing, a high-speed page compositionsystem, and the ability to perform multiple tasks at the same time. The monochrome version of thesytem is in regular daily production, while the color system is under development. 1ReferencesI. D.E. Troxel, "Automated Engraving of Gravure Cylinders," IEEE Trans. on Systems, Man andCybernetics," SMC-11, 9, November 1981, 585-596.RLE P.R. No. 124158

Cognitive Information Processing

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Cognitive Information Processing

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