Paper
8 February 2005 Color encoding for gamut extension and bit-depth extension
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Abstract
Monitor oriented RGB color spaces (e.g. sRGB) are widely applied for digital image representation for the simplicity in displaying images on monitor displays. However, the physical gamut limits its ability to encode colors accurately for color images that are not limited to the display RGB gamut. To extend the encoding gamut, non-physical RGB primaries may be used to define the color space, or the RGB tone ranges may be extended beyond the physical range. An out-of-gamut color has at least one of the R, G, and B channels that are smaller than 0 or higher than 100%. Instead of using wide-gamut RGB primaries for gamut expansion, we may extend the tone ranges to expand the encoding gamut. Negative tone values and tone values over 100% are allowed. Methods to efficiently and accurately encode out-of-gamut colors are discussed in this paper. Interpretation bits are added to interpret the range of color values or to encode color values with a higher bit-depth. The interpretation bits of R, G, and B primaries can be packed and stored in an alpha channel in some image formats (e.g. TIFF) or stored in a data tag (e.g. in JEPG format). If a color image does not have colors that are out of a regular RGB gamut, a regular program (e.g. Photoshop) is able to manipulate the data correctly.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Huanzhao Zeng "Color encoding for gamut extension and bit-depth extension", Proc. SPIE 5637, Electronic Imaging and Multimedia Technology IV, (8 February 2005); https://doi.org/10.1117/12.568467
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KEYWORDS
RGB color model

Computer programming

Printing

Digital imaging

Image storage

Quantization

Associative arrays

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