`dtmm.color`¶

Color conversion functions and utilities.

CMF creation function¶

load_cmf() : loads specter cmf data from file or pre-defined table
load_tcmf() : loads transmission cmf data from file or pre-defined table
cmf2tcmf() : converts cmf to transmission cmf.
srf2cmf() : converts spectral respone data to cmf
load_specter() : load specter from file or from data.
normalize_specter() : for specter normalization.

Color conversion¶

specter2color() : converts specter data to color RGB or gray image.
apply_gamma() : applies gamma curve to linear data
apply_srgb_gamma() : applies sRGB gamma curve to linear data
xyz2rgb() : Converts XYZ data to RGB
xyz2gray() : Converts XYZ data to YYY (gray)
spec2xyz() : Converts specter to XYZ

Module Contents¶

dtmm.color.apply_gamma(value, gamma)¶

apply_gamma(value, gamma)

Applies standard gamma function (transfer function) to the given (linear) data.

Parameters

value (float) – Input value
gamma (float) – Gamma factor

dtmm.color.apply_srgb_gamma(value)¶

apply_srgb_gamma(value)

Applies sRGB gamma function (transfer function) to the given (linear) data.

dtmm.color.xyz2srgb(xyz, rgb)¶

xyz2srgb(xyz)

Converts XYZ value to RGB value based on the sRGB working space with D65 reference white.

dtmm.color.xyz2gray(xyz, gray)¶

xyz2gray(xyz)

Converts XYZ value to Gray color

dtmm.color.spec2xyz(spec, cmf, xyz)¶

spec2xyz(spec,cmf)

Converts specter array to xyz value.

Parameters

spec (array_like) – Input specter data
cmf (array_like) – Color matching function

Returns

xyz – Computed xyz value.

Return type

ndarray

dtmm.color.specter2color(spec, cmf, norm=False, gamma=True, gray=False, out=None)¶

Converts specter data to RGB data (color or gray).

Specter shape must be […,k], where wavelengths are in the last axis. cmf must be a valid color matchin function array of size [k,3].

Parameters

spec (array) – Specter data of shape […, n] where each data element in the array has n wavelength values
cmf (array) – A color matching function (array of shape [n,3]) that converts the specter data to a XYZ color.
norm (bool or float, optional) – If set to False, no data normalization is performed (default). If True, internally, xyz data is normalized in the range [0,1.], so that no clipping occurs. If it is a float, data is normalized to this value.
gamma (bool or float, optional) – If gamma is True srgb gamma function is applied (default). If float is provided, standard gamma factor is applied with a given gamma value. If False, no gamma correction is performed.
gray (bool, optional) – Whether gray output is calculated (color by default)
out (array, optional) – Output array of shape (…,3)

Returns

rgb – A computed RGB value.

Return type

ndarray

Notes

Numpy broadcasting rules apply to spec and cmf.

Example

>>> cmf = load_tcmf()
>>> specter2color([1]*81, cmf)#should be close to 1,1,1
... 
array([0.99994901, 1.        , 0.99998533])

dtmm.color.srf2cmf(srf, out=None)¶

Converts spectral response function (Y) to color matching function (XYZ).

Parameters

srff (array_like) – Spectral response function of shape (…,n)
out (ndarray, optional) – Output array.

Returns

cmf – A color matching function array of shape (…,n,3)

Return type

ndarray

dtmm.color.normalize_specter(spec, cmf, out=None)¶

Normalizes specter based on the color matching function. (cmf array) so that calculated Y value is 1.

Parameters

spec (array_like) – Input illuminant specter data of shape (…,n).
cmf (array_like) – Color matching function of shape (…,n,3).
out (ndarray, optional) – Output array.

Returns

normalized_spec – A normalized version of the input specter

Return type

ndarray

Notes

Numpy broadcasting rules apply to spec and cmf.

dtmm.color.load_tcmf(wavelengths=None, illuminant='D65', cmf=CMF, norm=True, retx=False, single_wavelength=False)¶

Loads transmission color matching function.

This functions loads a CIE XYZ color matching function and transforms it to a transmission color matching function for a given illuminant. Resulting CMF matrix will transform unity into white color.

Parameters

wavelengths (array_like, optional) – Wavelengths at which data is computed. If not specified (default), original data from the 5nm tabulated data is returned.
illuminant (str, optional) – Name of the standard illuminant or path to illuminant data.
cmf (str, optional) – Name or path to the cmf function. Can be ‘CIE1931’ for CIE 1931 2-deg 5nm tabulated data, ‘CIE1964’ for CIE1964 10-deg 5nm tabulatd data, or ‘CIE2006-2’ or ‘CIE2006-10’ for a proposed CIE 2006 2- or 10-deg 5nm tabulated data.
norm (int, optional) – By default cmf is normalized so that unity transmission value over the full spectral range of the illuminant is converted to XYZ color with Y=1. You can disable this by setting norm = 0. If you set norm = 2, then the cmf is normalized for the interpolated spectra at given wavelengths, and not to the full bandwidth of the spectra (norm = 1).
retx (bool, optional) – Should the selected wavelengths be returned as well.
single_wavelength (bool, optional) – If specified, color matching function for single wavelengths specter is calculated by interpolation. By default, specter is assumed to be a piece-wise linear function and continuous between the specified wavelengts, and data is integrated instead.

Returns

cmf – Color matching function array of shape [n,3] or a tuple of (x,cmf) if retx is specified.

Return type

array

Example

>>> cmf = load_tcmf()
>>> specter2color([1]*81, cmf) #should be close to 1,1,1
... 
array([0.99994901, 1.        , 0.99998533])

dtmm.color.cmf2tcmf(cmf, spec, norm=True, out=None)¶

Converts CMF table to specter-normalized transmission CMF table

Parameters

cmf (array_like) – Color matchinf function array
spec (array_like) – Illuminant specter array
norm (bool, optional) – Whether to normalize illuminant specter before constructing the CMF.
out (ndarray, optional) – Output array

Returns

out – A transmission color matching function array.

Return type

ndarray

Notes

Numpy broadcasting rules apply to spec and cmf.

dtmm.color.load_specter(wavelengths=None, illuminant='D65', retx=False)¶

Loads illuminant specter data from file.

Parameters

wavelengths (array_like, optional) – Wavelengths at which data is interpolated
illuminant (str, or array, optional) – Name of the standard illuminant or filename. If specified as array, it must be an array of shape (n,2). The first column decribes wavelength and the second is the intensity.
retx (bool, optional) – Should the selected wavelengths be returned as well.

Returns

specter – Specter array of shape [num] or a tuple of (x,specter) if retx is specified

Return type

array

Examples

#D65 evaluated at three wavelengths >>> spec = load_specter((450,500,550), “D65”)

#illuminant with triangular specter evaluated at three wavelengths >>> spec = load_specter([450,475,500,], illuminant = [[400,0],[500,1],[600,0]])

dtmm.color.load_cmf(wavelengths=None, cmf=CMF, retx=False, single_wavelength=False)¶

Load XYZ Color Matching function.

This function loads tabulated data and re-calculates xyz array on a given range of wavelength values.

dtmm.color¶

CMF creation function¶

Color conversion¶

Module Contents¶

`dtmm.color`¶