uvfrom {spacesXYZ}

Convert from XYZ or xy to Uniform Chromaticity Spaces

Description

Convert from XYZ or xy to Uniform Chromaticity Spaces

Usage

uvfromXYZ( XYZ, space=1976 )

uvfromxy( xy, space=1976 )

Arguments

XYZ

a numeric Nx3 matrix with CIE XYZ coordinates in the rows, or a vector that can be converted to such a matrix, by row.

xy

a numeric Nx2 matrix with CIE xy coordinates in the rows, or a vector that can be converted to such a matrix, by row.

space

the year of the space of output uv desired - valid spaces are 1976 and 1960. The default space=1976 has largely superseded space=1960, but the latter is still used for computing Correlated Color Temperature; see CCTfromuv(). The 1976 space is used in the function LuvfromXYZ(). The 1960 coordinates are usually denoted by uv, and the 1976 coordinates by u'v'. The only difference is that v' = (3/2) v.

Value

a numeric Nx2 matrix with u'v' (or uv) coordinates in the rows.

For uvfromXYZ(), if X + 15Y + 3Z \le 0, uv are set to NA.

For uvfromxy(), if -2x + 12y + 3 \le 0, uv are set to NA.

The rownames are copied from input to output. If the input is invalid, the function returns NULL.

References

Wikipedia. CIE 1931 color space. https://en.wikipedia.org/wiki/CIE_1931_color_space

Wikipedia. CIE 1960 color space. https://en.wikipedia.org/wiki/CIE_1960_color_space

See Also

LuvfromXYZ(), standardXYZ()

Examples

# locate some standard illuminants on the 1976 UCS diagram
uvfromXYZ( standardXYZ( c('C','D50','D65','E')  ) )

##             u'        v'
##  C   0.2008921 0.4608838
##  D50 0.2091601 0.4880734
##  D65 0.1978398 0.4683363
##  E   0.2105263 0.4736842