Xerox 721P87491 manual Zero-width lines strokes, Curved shapes, Images

POSTSCRIPT

Zero-width lines (strokes)

Zero-width lines are lines that have a line width set to zero by the PostScript master. These lines may not image. The best method is to specify the sizes of the hairline you want, such as .24 setlinewidth instead of 0 setlinewidth.

Figure 2-5.Example illustrating fill function

Thickness

of Line

Center

Points of

Pixels

This illustration shows four rows of five pixels on the output device. The center points of the device pixels are at the cross sections of the dashed lines. The horizontal lines to be filled are indicated by two solid, bold line segments per horizontal line.

The horizontal line at the top contains the center points of the second row of pixels; therefore, the pixels are turned on by the imager. This is shown by cross hatching the pixels that are turned on. The horizontal line at the bottom of the picture does not contain the center points of the fourth row of pixels; therefore, no pixels are turned on, and the line is not visible.

Curved shapes

The flatness parameter is used to set the accuracy with which curves are rendered on the output device. Because DocuPrint does not use curve flattening (conversion of curves to line segments) in graphic rendering, the parameter for the operator setflat has no effect on the smoothness of curves.

Images

In DocuPrint, the region of the device space to be painted is determined according to the following rules:

•Scan Conversion paints only those pixels whose centers lie within the shape if:

—The resolution of the source image (sampled image) is higher than the device resolution. Scan Conversion paints those pixels whose centers lie within the shape.

2-20 XEROX DOCUPRINT NPS GUIDE TO USING PAGE DESCRIPTION LANGUAGES