Xerox DocuPrint Network Printer Series Guide Manual

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Xerox DocuPrint Network Printer Series Guide Manual Manual pdf 57 page image

POSTSCRIPTXEROX DOCUPRINT NPS GUIDE TO USING PAGE DESCRIPTION LANGUAGES 2-31ConsiderationsThe scan order of an image relative to the content of the image is notimportant. It is important that the scan order of the image in thedesired orientation is relative to the scan order of the page.There are circumstances when a transformation cannot be avoidedby any ordering of image data (such as when the image sides are notparallel to the sides of the paper, or when the image is skewed), butfor many cases a rotation can be avoided by ensuring that the datain the image is in the correct order.Ensuring optimum image data order is complicated by the fact thatthe rotations are not tied to the use of the rotate operator in aPostScript program, or to implied rotations in the image-to-userspace transformation. The transformations specified in PostScriptare part of a specification of the desired position of an image in termsof the default user coordinate system.DocuPrint NPS only performs an image rotation when one isrequired. Rotations of multiples of 90 degrees are optimized so thatthe impact is not too great.Because the data is already aligned with the printing orientation,DocuPrint NPS does not perform any rotation of the image. In thedefault user coordinate system, a rotate operation is required.Without the rotate operation, the PostScript specifies that the imagebe placed on the page with its left edge (fast scan dimension) parallelto the short edge of the paper. A 90 degree counterclockwise rotationof the coordinate system is needed to correctly specify the imageorientation on the page.It may be possible to arrange an appropriate order for the data bycorrectly arranging the original when a scan is performed. It isassumed that scanners produce data from a portrait scan in left-to-right (fast scan), top-to-bottom (slow scan) order.By rotating the original 90 degrees clockwise, you can obtain datafrom the scanner with the fast scan direction bottom-to-top (relativeto the original), and the slow scan direction left-to-right, matching thepage scan directions for the correct output orientation. Alternatively,you can have the data reordered by a program before the PostScriptmaster is created.After determining that a certain scan orientation produces data in theoptimum order for printing, you can scan an image and import it intoan emitter. Some rotation may be necessary to place the imagecorrectly.If the emitter performs a rotation by manipulating the data, then theresulting PostScript master may have the data in the incorrect order.It is also possible that the emitter may not alter the data and changethe transformations specified in PostScript so that the initial orderingis preserved.SummaryTo minimize imaging time, make sure that no data transformationsneed to be performed at the printer. Order the image data so that thefast and slow scan directions match the output fast and slow scandirections when the image is in the correct orientation on the page.With the image data correctly ordered, arrange the PostScripttransformations so that they specify the position and orientation of