DIRECTORY ImagerBitmapContext USING [Brick], ImagerTransformation USING [Transformation]; HBrick: CEDAR DEFINITIONS ~ BEGIN Transformation: TYPE ~ ImagerTransformation.Transformation; BrickShape: TYPE ~ RECORD [sSize, fSize, phase: CARD]; BrickShapeFromDeltas: PROC [s0, f0, s1, f1: INT] RETURNS [BrickShape]; BrickSpec: TYPE ~ RECORD [brickShape: BrickShape, m: Transformation]; BrickSpecFromTransformedRectangle: PROC [w, h: REAL, clientToDevice: Transformation, allowedRelativeError: REAL _ 0.05, minLevels: CARD _ 1] RETURNS [BrickSpec]; Brick: TYPE ~ ImagerBitmapContext.Brick; BrickFromDotScreen: PROC [pixelsPerDot: REAL, degrees: REAL, shape: REAL _ 0.5, allowedRelativeError: REAL _ 0.05, minLevels: CARD _ 16, maxSample: CARDINAL _ 255, pixelToDevice: Transformation _ NIL, trc: PROC [REAL] RETURNS [REAL] _ NIL] RETURNS [Brick]; FilterProc: TYPE ~ PROC [x, y: REAL] RETURNS [REAL]; BrickFromFilter: PROC [brickSpec: BrickSpec, filter: FilterProc, maxSample: CARDINAL _ 255, trc: PROC [REAL] RETURNS [REAL] _ NIL] RETURNS [Brick]; END. †HBrick.mesa Copyright c 1986 by Xerox Corporation. All rights reserved. Michael Plass, July 13, 1987 4:34:09 pm PDT For creating halftone bricks and tiles. BrickSpec.m is a perturbed version of clientToDevice that maps the brick exactly allowedRelativeError controls how close m ought to be to clientToDevice minLevels puts a lower limit on the number of pixels in the result pixelsPerDot is the number of "normalized" device pixels per halftone dot degrees is the counterclockwise rotation shape controls how elliptical the dots are; 0.0 and 1.0 give two different line screens, and 0.5 produces a dot symmetrical in x and y (before rotation). A shape parameter that is a little different from 0.5 usually gives a more uniform response curve. allowedRelativeError, minLevels as above maxSample is the maximum sample value in the output pixelToDevice specifies a transformation from the "normalized" device pixels do the actual device pixels; this is useful to account for different scan directions and to allow for differing resolutions in the two directions. trc is a specification of the desired output-to-input mapping effected by the brick; it should map the interval [0.0..1.0] monotonically onto itself. A filter function defined on x in [-1..+1], y in [-1..+1], returning values over any range. Calls the FilterProc to generate the samples; linearizes the result. maxSample and trc are as above Ê˜codešœ™Kšœ Ïmœ1™