2.2.2.11 LogColorSpace Object

The LogColorSpace Object specifies a logical color space for the playback device context, which can be the name of a color profile in ASCII characters.

Signature (4 bytes): A 32-bit unsigned integer that specifies the signature of color space objects; it MUST be set to the value 0x50534F43, which is the ASCII encoding of the string "PSOC".

Version (4 bytes): A 32-bit unsigned integer that defines a version number; it MUST be 0x00000400.

Size (4 bytes): A 32-bit unsigned integer that defines the size of this object, in bytes.

ColorSpaceType (4 bytes): A 32-bit signed integer that specifies the color space type. It MUST be defined in the LogicalColorSpace Enumeration (section 2.1.1.14). If this value is LCS_sRGB or LCS_WINDOWS_COLOR_SPACE, the sRGB color space MUST be used.

Intent (4 bytes): A 32-bit signed integer that defines the gamut mapping intent. It MUST be defined in the GamutMappingIntent Enumeration (section 2.1.1.11).

Endpoints (36 bytes): A CIEXYZTriple Object (section 2.2.2.7) that defines the CIE chromaticity x, y, and z coordinates of the three colors that correspond to the RGB endpoints for the logical color space associated with the bitmap. If the ColorSpaceType field does not specify LCS_CALIBRATED_RGB, this field MUST be ignored.

GammaRed (4 bytes): A 32-bit fixed point value that defines the toned response curve for red. If the ColorSpaceType field does not specify LCS_CALIBRATED_RGB, this field MUST be ignored.

GammaGreen (4 bytes): A 32-bit fixed point value that defines the toned response curve for green. If the ColorSpaceType field does not specify LCS_CALIBRATED_RGB, this field MUST be ignored.

GammaBlue (4 bytes): A 32-bit fixed point value that defines the toned response curve for blue. If the ColorSpaceType field does not specify LCS_CALIBRATED_RGB, this field MUST be ignored.

Filename (260 bytes): An optional, ASCII charactger string that specifies the name of a file that contains a color profile. If a file name is specified, and the ColorSpaceType field is set to LCS_CALIBRATED_RGB, the other fields of this structure SHOULD be ignored.

The Endpoints, GammaRed, GammaGreen, and GammaBlue fields are used to specify a logical color space. The Endpoints field is a CIEXYZTriple Object that contains the x, y, and z values of the RGB endpoint of the color space.

The relation between tri-stimulus values X,Y,Z and chromaticity values x,y,z is expressed as follows.

 x = X/(X+Y+Z)
 y = Y/(X+Y+Z)
 z = Z/(X+Y+Z)
            

The GammaRed, GammaGreen, and GammaBlue fields contain values in "8.8 fixed point" format, which is a technique for representing non-integer numbers. Each value consists of a zero-extended 8-bit magnitude followed by an 8-bit fraction, with the combined 16 bits left-shifted by 8 bits. Thus, in 32-bits, the real value N.F is 00000000nnnnnnnnffffffff00000000, where "nnnnnnnn" and "ffffffff" are binary representations of N and F, respectively. For example, for the real number 10.5, nnnnnnnn would be 00001010 (binary 10) and ffffffff would be 00000101 (binary 5), and the complete 32-bit binary value would be 00000000000010100000010100000000, which is the hexadecimal value 0x0A50.