Subpixel rendering: from font rendering to image subsampling [Applications Corner]

Subpixel rendering technologies take advantage of the subpixel structure of a display to increase the apparent resolution and to improve the display quality of text, graphics, or images. These techniques can potentially improve the apparent resolution because a single pixel on color liquid crystal display (LCD) or organic light-emitting diode (OLED) displays consists of several independently controllable colored subpixels. Applications of subpixel rendering are font rendering and image/video subsampling. By controlling individual subpixel values of neighboring pixels, it is possible to microshift the apparent position of a line to give greater details of text. Similarly, since the individual selectable components are increased threefold by controlling subpixels rather than pixels, subpixel-based subsampling can potentially improve the apparent resolution of a down-scaled image. However, the increased apparent luminance resolution often comes at the price of color fringing artifacts. A major challenge is to suppress chrominance distortion while maintaining apparent luminance sharpness. This column introduces subpixel arrangement in color displays, how subpixel rendering works, and several practical subpixel rendering applications in font rendering and image subsampling.