acknowledgements for ansi/nist-itl 1-2011 - NIST Visual Image ...

ANSI/NIST-ITL 1-2011 - UPDATE 2013 DRAFT VERSIONIn versions of this standard prior to 2007, the term “color space” referred to devicedependentcolor information with a particular sequence and range for the three colorchannels. The choice was either RGB or an RGB-derivative space known as YCC. Neitherspace provides an objective definition of a particular color or relates to the way in whichhumans perceive color. For JPEG-compressed color images stored in the JFIF format, thepreferred (external) color space is sRGB and an entry of “SRGB” shall be used. AlthoughsRGB is the preferred color space for compressed images for this version, in the 2000version of this standard, it was stated that “the preferred color space for compressed imagesusing baseline JPEG and JFIF is YCbCr to be coded as ‛YCC’,” while the color space foruncompressed color images was to be labeled RGB. Therefore, for backward compatibilitypurposes, new systems shall accommodate JPEG images that have been labeled as using theYCC color space. Systems conforming to this standard shall accept an entry of YCC andinterpret it as meaning a (device-dependent) RGB color space.For JPEG 2000 images stored in the JP2 file format, the available enumerated color spacesare sRGB, sYCC, and grayscale. The preferred (external) color space for color images issRGB. If a photo acquisition device uses another International Color Consortium 42 (ICC)color profile, the acquisition system shall convert the image data to the sRGB, sYCC, orgrayscale color space before the JP2 file may be embedded in a record.To ensure that color images exchanged between differing systems can be correctly displayedor printed, images should be converted to the device-independent color space, sRGB, beforecompression or transmission to another system. As defined by IEC 61966-2-1, sRGB is anon-linear display profile that accommodates the voltage-to-color response characteristics ofmost high quality CRT monitors. The colors of the red, green, and blue phosphors(primaries) and the white point setting of an sRGB-conformant monitor are specified in theIEC document. For uncompressed color images containing non-interleaved red, green andblue pixels in that order, the preferred color space is sRGB. Typically, modern digitalcameras, desktop scanners, LCD monitors, and printers, although they do not inherentlyoperate in sRGB space, are designed with circuitry or software to produce sRGB output orto accommodate sRGB as an input space. If an image acquisition device’s color space isunknown, sRGB is usually a reasonable choice. If an acquisition device and its softwarecannot provide sRGB output, various color management products are availablecommercially that use its color profile, often available from its manufacturer, to convertimages in its native color space to sRGB.7.7.11 Eye colorThis information appears in Field 10.027: Subject eye color / SEC and in Field 17.020:Eye color / ECL. The eye color describes the eye color of the subject as seen in the image.If unusual or unnatural, such as is the case when colored contact lenses are present and the‘real’ eye color cannot be ascertained, then the color shall be labeled as “XXX”. For nearinfra-red (NIR) images, if this field is entered, it shall be 'XXX'. Values for these fields shallbe the alphabetic entries in the “Attribute code” column of Table 17.42See http://www.color.org/May, 2013 DRAFT VERSION UPDATE 2013 Page 91