lookup table (LUT)
In general, a Lookup Table (LUT) is a value table or assignment table for complex and non-linear functions. Pre-calculated values are entered into a LUT table, which require a high computational effort. This can be reduced by the fact that one does not accomplish a computation with the value determination, but directly accesses the values registered in the Lookup Table. This applies especially to non-linear curves or 3D models with different parameters and characteristics, but also to the evaluation and correction of color spaces and gradation curves of displays and other output devices.
A lookup table is generally a matrix-likevalue table from which values can be assigned to each other. For example, you can use it to read values for the field strength of a transmitter at a certain time of day, or the temperature of a component at a certain power level. Instead of the tabular form, the values can also be taken from non-linear characteristic cur ves, the lookup characteristic curves. One enters the Y-value and can then read the resulting X-value.
Since lookup tables can reduce the computational effort, they are used wherever nonlinear functions influence the relationships between two or more characteristic values. For example, in digitalimage processing and medical technology to improve contrast, brightness or color reproduction.
In peripheral devices, the ICC color profiles are a technique for matchingcolor spaces and color models. This technique can be supported by Lookup Tables (LUT). Such a Lookup Table is a tabular listing of colors. Depending on the color model used, it can be the three primary colorsred, green, blue, which are entered into this table with their intensity values. With a color depth of 8 bits per pixel, values between 0 and 255 are entered for the respective primary colors. If the color values for red, green and blue are identical, the color signal is achromatic. The individual colors are interpreted as indices of the color index table( CLUT).
Just like the color index values for color displays, gradation values for gamma corrections with low or high resolution can also be stored in a value table.