[_CDMiwok_01_]<bonsai2.0>cedar>release>Imager>ImagerBrick.mesa!1

ImagerBrick.mesa

Michael Plass, January 13, 1992 2:33 pm PST

For creating halftone bricks and tiles.

DIRECTORY

ImagerSample USING [SampleMap],

ImagerTransformation USING [Transformation],

Prop USING [PropList];

ImagerBrick: CEDAR DEFINITIONS

~ BEGIN

Brick Shape

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];

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

Bricks

Brick: TYPE ~ RECORD [maxSample: CARDINAL, sampleMap: ImagerSample.SampleMap, phase: NAT];

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];

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.

FilterProc: TYPE ~ PROC [x, y: REAL] RETURNS [REAL];

A filter function defined on x in [-1..+1], y in [-1..+1], returning values over any range.

BrickFromFilter: PROC [brickSpec: BrickSpec, filter: FilterProc, maxSample: CARDINAL ¬ 255, trc: PROC [REAL] RETURNS [REAL] ¬ NIL] RETURNS [Brick];

Calls the FilterProc to generate the samples; linearizes the result.

maxSample and trc are as above

Halftone Specifications

This is a convenient centralized place for these types.

Toner: TYPE ~ MACHINE DEPENDENT {black, cyan, magenta, yellow, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15};

HalftoneProperties: TYPE ~ LIST OF HalftonePropertiesForSeparation;

HalftonePropertiesForSeparation: TYPE ~ RECORD [type: ATOM, toner: Toner, brick: ImagerBrick.Brick, propList: Prop.PropList ¬ NIL];

The type distingishes classes of bricks for various kinds of color.

END.