Technical Features New To Windows Vista - Print - XPS Print Path

XPS Print Path

The XPS Print Path introduced in Windows Vista supports high quality 16-bit color printing. The XPS print path uses XML Paper Specification (XPS) as the print spooler file format, that serves as the page description language (PDL) for printers. The XPS spooler format is the intended replacement for the Enhanced Metafile (EMF) format which is the print spooler format in the Graphics Device Interface (GDI) print path. XPS is an XML-based (more specifically XAML-based) color-managed device and resolution independent vector-based paged document format which encapsulates an exact representation of the actual printed output. XPS documents are packed in a ZIP container along with text, fonts, raster images, 2D vector graphics and DRM information. For printers supporting XPS, this eliminates an intermediate conversion to a printer-specific language, increasing the reliability and fidelity of the printed output. Microsoft claims that major printer vendors are planning to release printers with built-in XPS support and that this will provide better fidelity to the original document.

At the core of the XPS print path is XPSDrv, the XPS-based printer driver which includes the filter pipeline. It contains a set of filters which are print processing modules and an XML-based configuration file to describe how the filters are loaded. Filters receive the spool file data as input, perform document processing, rendering and PDL post-processing, and then output PDL data for the printer to consume. Filters can perform a single function such as watermarking a page or doing color transformations or they can perform several print processing functions on specific document parts individually or collectively and then convert the spool file to the page description language supported by the printer.

Windows Vista also provides improved color support through the Windows Color System for higher color precision and dynamic range. It also supports CMYK colorspace and multiple ink systems for higher print fidelity. The print subsystem also has support for named colors simplifying color definition for images transmitted to printer supporting those colors.

The XPS print path can automatically calibrate color profile settings with those being used by the display subsystem. Conversely, XPS print drivers can express the configurable capabilities of the printer, by virtue of the XPS PrintCapabilities class, to enable more fine-grained control of print settings, tuned to the individual printing device.

Applications which use the Windows Presentation Foundation for the display elements can directly print to the XPS print path without the need for image or colorspace conversion. The XPS format used in the spool file, represents advanced graphics effects such as 3D images, glow effects, and gradients as Windows Presentation Foundation primitives, which are processed by the printer drivers without rasterization, preventing rendering artifacts and reducing computational load. When the legacy GDI Print Path is used, the XPS spool file is used for processing before it is converted to a GDI image to minimize the processing done at raster level.