In many case, the data set to be visualized is generally a
discrete grid data, while data between the grid could be got by
using the interpolation method. Drawing module of the
visualization system generally does not directly interpolated
data in the grid, but to use the functionality provided by the
computer hardware directly to the RGB color value of the color
interpolation calculation. The actual color table can be used to
solve this problem, because the color table index is completely
linear mapping between the data and the colors. Generally the
index is the row number in color map.