Truecolor
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It has been suggested that this article or section be merged into RGB color model#The 24-bit RGB representation. (Discuss) |
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1-bit monochrome 8-bit color |
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- See also True Colors (disambiguation).
Truecolor is a method of representing and storing graphical image information (especially in computer processing) in an RGB color space such that a very large number of colors, shades, and hues can be displayed in an image, such as in high quality photographic images or complex graphics. Usually, truecolor is defined to mean at least 256 shades of red, green, and blue, for a total of at least 16,777,216 color variations. Truecolor can also refer to an RGB display mode that does not need a color look-up table (CLUT).[1]
For each pixel, generally one byte is used for each channel while the fourth byte (if present) is being used either as an alpha channel data or simply ignored. Byte order is usually either RGB or BGR. However, systems do exist with more than 8 bits per channel, and these are often also referred to as truecolor (for example a 48-bit truecolor scanner).
One byte (eight bits) per channel permits 256 (28) intensities for each of the color channels. This allows 16,777,216 (224) colors for each pixel (often approximated as 16 million, because 220 is close to 106; although the true number is closer to 17 million). The human eye is popularly believed to be capable of discriminating among as many as ten million colors.[2]
Thirty-two bit truecolor can hold an alpha channel, which gives the pixel's degree of transparency (versus opacity) for representing translucent images (and is often a requirement for hardware acceleration of such drawing) allowing desktop environments to more easily provide effects such as translucent windows, fading menus, and shadows.
In a framebuffer, an alpha channel is meaningless, but 32-bit truecolor is often used because it makes pixel addressing easier. Addressing an array of 24-bit pixels requires multiplication by three, which is more computationally expensive than multiplication by four, which can be computed by bit shifting.
The above explanation is more or less from a Microsoft viewpoint, as Windows is the most common desktop operating system, and it refers to the 24-bit per pixel color mode as truecolor. But, truecolor can also refer to a display mode that does not need a color look-up table (CLUT). Thus, truecolor can be used with any color depth (e.g. 8-bit, 16-bit, 24-bit, ...) but only without a CLUT. However, RGB encodings with only five or six bits per color channel are typically called "highcolor" or "thousands of colors", while color depths of 8-bits or less usually do employ a CLUT.
[edit] See also
- Planar
- Chunky
- Deep Color
- Highcolor
- Truecolor (color depth)
- List of monochrome and RGB palettes — 24-bit RGB section.
[edit] References
- ^ Charles A. Poynton (2003). Digital Video and HDTV. Morgan Kaufmann. p. 36. ISBN 1558607927. http://books.google.com/books?id=ra1lcAwgvq4C&pg=RA1-PA36&dq=truecolor&lr=&as_brr=0&as_pt=ALLTYPES&ei=MT79ScjqLoPWkAS87eXPBA#PRA1-PA36,M1.
- ^ Color in Business, Science and Industry. Wiley Series in Pure and Applied Optics (third edition ed.). New York: Wiley-Interscience. 1975. pp. 388. ISBN 0471452122.
