Source code for colormath.density

# -*- coding: utf-8 -*-
Formulas for density calculation.

from math import log10
from colormath.density_standards import ANSI_STATUS_T_BLUE, ANSI_STATUS_T_GREEN, \

[docs]def ansi_density(color, density_standard): """ Calculates density for the given SpectralColor using the spectral weighting function provided. For example, ANSI_STATUS_T_RED. These may be found in :py:mod:`colormath.density_standards`. :param SpectralColor color: The SpectralColor object to calculate density for. :param numpy.ndarray density_standard: NumPy array of filter of choice from :py:mod:`colormath.density_standards`. :rtype: float :returns: The density value for the given color and density standard. """ # Load the spec_XXXnm attributes into a Numpy array. sample = color.get_numpy_array() # Matrix multiplication intermediate = sample * density_standard # Sum the products. numerator = intermediate.sum() # This is the denominator in the density equation. sum_of_standard_wavelengths = density_standard.sum() # This is the top level of the density formula. return -1.0 * log10(numerator / sum_of_standard_wavelengths)
[docs]def auto_density(color): """ Given a SpectralColor, automatically choose the correct ANSI T filter. Returns a tuple with a string representation of the filter the calculated density. :param SpectralColor color: The SpectralColor object to calculate density for. :rtype: float :returns: The density value, with the filter selected automatically. """ blue_density = ansi_density(color, ANSI_STATUS_T_BLUE) green_density = ansi_density(color, ANSI_STATUS_T_GREEN) red_density = ansi_density(color, ANSI_STATUS_T_RED) densities = [blue_density, green_density, red_density] min_density = min(densities) max_density = max(densities) density_range = max_density - min_density # See comments in for VISUAL_DENSITY_THRESH to # understand what this is doing. if density_range <= VISUAL_DENSITY_THRESH: return ansi_density(color, ISO_VISUAL) elif blue_density > green_density and blue_density > red_density: return blue_density elif green_density > blue_density and green_density > red_density: return green_density else: return red_density