[This is preliminary documentation and subject to change.]
Recognizing the need for standard, device-independent color measurements, the Commission International de l'Eclairage (International Commission on Illumination), or CIE, created a color space based on "imaginary" primary colors. No actual device is expected to produce colors in this color space. It is used as a means of converting colors from one color space to another. The primary colors in this color space are the abstract colors X, Y, and Z.
The CIE XYZ color space is widely used as the basis for color space conversion. With the rise of the Internet, however, bandwidth considerations have made the XYZ color space unwieldy. The exchange of images over the limited bandwidth of the Internet necessitates a more compact color model.
As a result, Hewlett-Packard and Microsoft have proposed the adoption of a standard predefined RGB color space known as sRGB, so as to allow accurate color management with very little data overhead. A white paper discussing the technical issues involved in sRGB is available on the Internet at:
http://www.color.org/contrib/sRGB.html
A help-file version of the white paper, sRGB.HLP, is also available in the \Help folder of the ICM 2.0 Programmer's Reference in the Platform SDK.
Different file formats may use or add a flag to specify that the image is in sRGB color space. In the Windows device-independent bitmap (DIB) format, setting the bV5CSType member of the BITMAPV5HEADER structure to LCS_sRGB specifies that the DIB colors are in the sRGB color space.