Font rasterization is the process of converting text from a vector description (as found in scalable fonts such as TrueType fonts) to a raster or bitmap description. This often involves some anti-aliasing on screen text to make it smoother and easier to read. It may also involve "hinting", that is, the use of information precomputed for a particular font size. Example showing effect of vector graphics on ppm scale: (a) original vector-based illustration; (b) illustration magnified 8x as a vector image; (c) illustration magnified 8x as a raster image. ... TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobes Type 1 fonts used in PostScript. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ... For the use of the term raster in radio regulation, see frequency raster. ... In digital signal processing, anti-aliasing is the technique of minimizing aliasing (jagged or blocky patterns) when representing a high-resolution signal at a lower resolution. ... A font test with (lower rows) and without hinting (upper rows) at 100% (above) and 400% (below). ...

Types of rasterization

Aliasing and ClearType anti-aliasing.

In modern operating systems, rasterization is normally provided by a shared library common to many applications. Such a shared library may be built in to the operating system or the desktop environment, or it may be added at some later time. In principle, each application may use a different font rasterization library, but in practice most systems attempt to standardize on a single library. Shows two examples of onscreen text. ... In computer science, a library is a collection of subprograms used to develop software. ... An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ... It has been suggested that Desktop metaphor,Paper paradigm be merged into this article or section. ...

In older systems and in some embedded systems, fonts are represented as bitmaps pre-drawn at specific sizes. However, most modern systems use fonts represented as mathematical primitives, allowing arbitrary scalability. For the use of the term raster in radio regulation, see frequency raster. ...

Simple rasterization without antialiasing

The simplest form of rasterization is simple line-drawing with no antialiasing of any sort. This is the fastest method (that is, it requires the least computation to place on screen). This approach has the disadvantage that glyphs may lose their definition when rendered at small sizes. Therefore, many fonts contain "hints" which aid the system's rasterizer in deciding where to render pixels for particularly troublesome areas in the glyphs, or sets of hand-tweaked bitmaps to be used at specific pixel sizes. Simple rasterization, with no antialiasing. ... Simple rasterization, with no antialiasing. ...

Rasterization with antialiasing

A more complicated approach is to use standard anti-aliasing techniques from computer graphics. This can be thought of as determining, for each pixel, how much of that pixel is occupied by the letter, and drawing that pixel with that degree of opacity. For example, when drawing a black letter on a white background, if a pixel ideally should be half filled (perhaps by a diagonal line from corner to corner) it would be drawn in 50% gray. Simple application of this procedure can lead to somewhat blurry glyphs: for example, if the letter includes a vertical line which should be one pixel wide but falls exactly between two pixels, it will appear on screen a two-pixel-wide gray line. This blurriness is a tradeoff of clarity for accuracy. Some systems demonstrate the opposite sacrifice by using hinting to force lines to fall within integral pixel coordinates. Rasterization without antialiasing or hinting This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ... Rasterization without antialiasing or hinting This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ...

Rasterization with subpixel rendering for an RGB flat panel display

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; Microsoft's proprietary implementation goes by the name ClearType. Rasterization with hinted subpixel rendering for an RGB flat panel screen This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ... Rasterization with hinted subpixel rendering for an RGB flat panel screen This is a screenshot of a copyrighted website, video game graphic, computer program graphic, television broadcast, or film. ... Subpixel rendering works by increasing the luminance reconstruction points of a color subpixelated screen, such as a liquid crystal display (LCD). ... ClearType is a registered trademark for a technology developed by Microsoft Corporation to improve the appearance of text on certain types of computer display screens, especially flat-panel displays. ...

Detail of subpixel rendering, showing positions of individual color pixels

Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ...

Currently used rasterization systems

Windows uses a combination of font-level hinting and antialiasing. Since Windows XP, it has also supported subpixel rendering. The Windows rasterizer is an example of one that prioritizes clarity; by forcing text into integral coordinate positions (and not even antialiasing certain fonts at certain sizes), it becomes easier to read on the screen, but often bears little resemblance to the font as printed. Microsoft Windows is the name of several families of proprietary operating systems by Microsoft. ... Windows XP is a line of proprietary operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. ...

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 more accurately. 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. Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ... Quartz is the marketing name of the proprietary graphics layer that sits on top of the open source Darwin core of Mac OS X. Quartz is part of the Core Graphics framework. ...

RISC OS uses its own font rendering system, with features such as scaffolding and hinting, sub-pixel anti-aliasing and background blending [1]. This article or section does not cite its references or sources. ...

Most other systems use the FreeType library, which falls somewhere between Microsoft's and Apple's implementations; it supports hinting and anti-aliasing, and optionally performs subpixel rendering. Due to problems with patent licensing, many binary distributions of it do not support hinting non-Free fonts with the same quality as the Windows and OS X rasterizers, although the functionality is present and easily enabled. The Free fonts included with most Linux distributions look better with FreeType's "auto-hinting" mode, which is high-quality and not encumbered by patents. FreeType is a software library that implements a font engine. ...

D-Type Font Engine is an independent, proprietary and portable font rasterization library. It provides anti-aliasing, subpixel precision, automatic hinting, bitmap filtering and other techniques that can improve the appearance and legibility of text on screen. According to the authors, the display quality of D-Type Font Engine can be configured to match or exceed the quality of Windows and Mac OS X font rasterizers while using only non-hinted TrueType, OpenType or Type 1 fonts.