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LUT refers to display look-up table (Look-Up-Table), which is essentially a RAM. After it writes the data into RAM in advance, every time a signal is input, it is equivalent to input an address to look up the table, find out the content corresponding to the address, and then output.

At present, FPGAs mostly use 4-input LUTs, so each LUT can be regarded as a RAM with 4-bit address lines.



The application range of LUT is relatively wide, for example: LUT (Look-Up Table) can be applied to a mapping table of pixel gray value, it will actually sample the pixel gray value after a certain transformation such as threshold, inversion, two Value, contrast adjustment, linear transformation, etc., have become another corresponding gray value, which can play a role in highlighting the useful information of the image and enhancing the light contrast of the image. Many PC series cards have 8/10/12/16 or even 32-bit LUT. The specific conversion in the LUT is defined by the software. The most important significance of LUT here is that it is compatible with the high-end display functions of ordinary monitors, so that those wide color gamuts (generally more than srgb) that cannot be displayed by ordinary monitors can be roughly simulated on ordinary monitors. However, the effect simulated by lut can only be used as a reference, as a rough look and feel when retouching. The best and most complete presentation is still highly consistent with the indicators of the display, graphics card and material itself, so-called "hard decoding".

LUT: Local User Terminal (local communication terminal)

Since desktop publishing came to the computer, the monitor has become one of the important devices in the prepress process. The existence of the monitor can also be found in the processes of scanning, digital photography, photo modification, and typesetting. However, many peers often ignore a part of the display, but if there is an image, they don't care whether the color of the screen is correct. Know if a color accurate (or more accurate) display can be used as SoftProofing (with additional printed ICCProfile) to help employees improve the color quality of the product, and also save costs for the company. Fortunately, color management has become popular in recent years, and monitor calibration has begun to be taken seriously.

Product related

There are monitor calibration systems of different grades on the market, some only have software, some software is combined with hardware (colorimeter or spectrophotometer), and some even sell the monitor together. The prices also range from free to more than 60,000 yuan. Of course, the effects of each system are also different. Users should first understand the differences between different systems and whether they can achieve the desired results. In fact, all display adjustment systems can be divided into two categories, namely the additional adjustment system (there are divided into full software "or human eye" adjustment and two kinds of instrument calibration such as colorimeter or spectrophotometer) and the built-in Adjust the system.

The biggest difference between the two is that the additional adjustment system can't adjust the color of the display, but the lookup table (abbreviated as LUT) in the display card in the computer is adjusted to achieve the desired color. So what is a LUT? Before understanding the LUT, let us see what is adjusted when adjusting the display. We do not calibrate the monitor to match the process color. Because the color gamut of the display is RGB, the color is formed by the additive color method, and the color is formed by the radiation, and the printing is CMYK, the color is formed by the subtractive color method, and the color is formed by reflection. Therefore, the two are totally unrelated, so it is impossible for us to adjust the display to the same color as the print.


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