DIRECTORYImagerMasks, ImagerBasic, ImagerBrick;ImagerHalftone: CEDAR DEFINITIONS ~ BEGINTransformation: TYPE ~ ImagerBasic.Transformation;PixelArray: TYPE ~ ImagerBasic.PixelArray;PixelBuffer: TYPE ~ ImagerBasic.PixelBuffer;Brick: TYPE ~ ImagerBrick.Brick;Mask: TYPE ~ ImagerMasks.Mask;DeviceBrick: TYPE ~ REF DeviceBrickRep;DeviceBrickRep: TYPE ~ RECORD [fMin, sMin: INTEGER,fPeriod: NAT,phase: NAT,seq: SEQUENCE sPeriod: NAT OF PixelBuffer];MakeDeviceBrick: PROC [brick: Brick, maxPixelValue: CARDINAL] RETURNS [d: DeviceBrick];MakeSquareBrick: PROC [size: NAT, p, q: INTEGER, pModulation, qModulation: REAL, maxPixelValue: CARDINAL] RETURNS [DeviceBrick];Halftone: PROC [dest: Mask, mask: Mask, source: PixelArray, transformation: Transformation, deviceBrick: DeviceBrick];DotScreen: PROC [x, y: REAL] RETURNS [fvalue: REAL];LineScreen: PROC [x, y:REAL] RETURNS [fvalue: REAL];END.   ╛  ImagerHalftone.mesaMichael Plass, July 11, 1983 3:56 pmData typesOperationsMakes a square device brick with zero phase.  Will return a dot screen if pModulation = qModulation > 0, a line screen if one of these is zero, otherwise something in between a dot and line screen.  The screen angle will be arctan (p/q), and the period will be size/sqrt(p*p+q*q).The tranformation takes PixelArray space to device space: [x y 1] T = [s f 1]. Э╩x  Ш JЩJЩ$JШ Ъ╧k	Ш	JЪЬ%Ш%JШЧJШ JЪЬЭШ)head2Щ
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