of paper. Most computer displays have pixels made up of multiple subpixels (typically one each for red, green, and blue, which are combined to produce the full range of colours). In some cases, particularly with flat panel displays, it is possible to exploit this by rendering at the subpixel resolution rather than using whole pixels, which can increase the effective resolution of the screen. This is generally known as subpixel rendering. One proprietary implementation of subpixel rendering is Microsoft's ClearType. Currently used rasterization systems In modern operating systems, rasterization is normally provided by a shared library common to many applications. Such a shared library may be built into the operating system or the desktop environment, or may be added later. In principle, each application may use a different font rasterization library, but in practice most systems attempt to standardize on a single library. Microsoft Windows has supported subpixel rendering since Windows XP. On the other hand, the standard Microsoft rasterizer without ClearType is an example of one that prioritizes type designer's intent of clarity; by forcing text into integral coordinate positions, following the type designer's intent of hinting, and even not antialiasing certain fonts at certain sizes, following the type designer's intent of the gasp table, it becomes easier to read on the screen, but may appear somewhat different when printed. This has changed with Direct2D/DirectWrite shipping on Windows 7 and Windows Vista platform update. Mac OS X's Quartz is distinguished by the use of floating-point positioning ; it does not force glyphs into exact pixel locations, instead using various antialiasing techniques, including subpixel rendering, to position characters and lines to appear further from the type designer's intent of hinting and closer to the original outline. The result is that the on-screen display looks extremely similar to printed output, but can occasionally be difficult to read at smaller point sizes. Most other systems use the FreeType library, which depending on the render mode, falls anywhere between Microsoft's and Apple's implementations; it supports hinting and anti-aliasing, and optionally performs subpixel rendering. References External links The Raster Tragedy at Low-Resolution Revisited – Beat Stamm's online book about rasterization, with an emphasis on ClearType CS 354 Computer Graphics — path rendering; University of Texas at Austin Texts Rasterization Exposures The Ails Of Typographic Anti-Aliasing Rasterization