Search results
Results from the WOW.Com Content Network
The chromatic adaptation matrix in the diagonal von Kries transform method, however, operates on tristimulus values in the LMS color space. Since colors in most colorspaces can be transformed to the XYZ color space, only one additional transformation matrix is required for any color space to be adapted chromatically: to transform colors from ...
where is the cone sensitivity matrix and is the spectrum of the conditioning stimulus. This leads to the von Kries transform for chromatic adaptation in LMS color space (responses of long-, medium-, and short-wavelength cone response space):
The elements of the diagonal matrix D are the ratios of the cone responses (Long, Medium, Short) for the illuminant's white point. The more complete von Kries transform, for colors represented in XYZ or RGB color space, includes matrix transformations into and out of LMS space, with the diagonal transform D in the middle. [6]
It is argued that this aids color constancy, especially in the blue region. (Compare Finlayson et al. 94, Spectral Sharpening:Sensor Transformations for Improved Color Constancy) Perform chromatic adaptation using CAT02 (also known as the "modified CMCCAT2000 transform"). Convert to an LMS space closer to the cone fundamentals.
Color constancy is, in turn, related to chromatic adaptation. Conceptually, color balancing consists of two steps: first, determining the illuminant under which an image was captured; and second, scaling the components (e.g., R, G, and B) of the image or otherwise transforming the components so they conform to the viewing illuminant.
A uniform color space (UCS) is a color model that seeks to make the color-making attributes perceptually uniform, i.e. identical spatial distance between two colors equals identical amount of perceived color difference. A CAM under a fixed viewing condition results in a UCS; a UCS with a modeling of variable viewing conditions results in a CAM.
As the LMS algorithm does not use the exact values of the expectations, the weights would never reach the optimal weights in the absolute sense, but a convergence is possible in mean. That is, even though the weights may change by small amounts, it changes about the optimal weights.
The levels of excitation of each cone type are the parameters that define LMS color space. To calculate the opponent process tristimulus values from the LMS color space, the cone excitations must be compared: [citation needed] The luminous opponent channel is equal to the sum of all three cone cells (plus the rod cells in some conditions).