## 2 Methods of Pseudo-Coloring with the RGB Palette  
The range of electromagnetic waves (visible light) detected by the human sense of sight includes waves with a length of about 380 nm to 770 nm. This entire range is called white light, resulting from the mixing of seven primary colors (Figure 1). Light waves, after passing through the optical system of the eye, create a kind of image on the retina, the light-sensitive membrane located at the back of the eye. The retina consists of two types of receptors:  
* rods: highly photosensitive, responsible for night vision, shape and movement detection;
* cones: less photosensitive, responsible for day vision, detecting details and colors. There are about 100 million rods, and only 6 million cones and they are concentrated mainly in the macula. We owe color vision to cones. There are three types of cones in the human retina, each of which has a different spectral characteristic, i.e., a different  
Figure 1: Basic colors. sensitivity for each wavelength of light. These three types of cones (Figure 2) are denoted as S (maximum response for short waves), M (maximum response for medium waves), and L (maximum response for long waves) [1,2]. S cones have a maximum sensitivity for a wavelength of approx. 445 nm, which corresponds to the blue color (B). It is practically incapable of detecting wavelengths longer than 520 nm. M cones are \"tuned\" to wavelengths of 535 nm (green, G), and L cones to 575 nm, which in turn corresponds to yellow, although it is customary to assume red (R). The individual colors perceived by humans are created as a result of the interaction of nerve impulses produced by all three types of cones. The signals produced by the cones pass through several layers of neurons in the retina and then via the optic nerves, first to the lateral geniculate nucleus (LGN) and finally to the occipital lobe of the brain. The LGN receives input from the three types of cones and produces three different output channels: one achromatic (brightness) channel summing the L (Red) and M (Green) cone outputs, and two chromatic channels which in turn subtract the L (Red) and M (Green) cone output pulses, or subtract the achromatic (Yellow) channel output and the S (Blue) cone output pulses (Figure 3). It is estimated that the ratio of the number of cones of each type is R:G:B = 40:20:1. It can be seen that the resultant sensitivity of the human eye is the lowest for the blue color. Figure 3: The method of formation of input channels for LGN. Figure 2: The relative sensitivity of the cones of the human eye. The properties of the human eye related to the perception of colors are reflected in one of the color space models, the RGB model (Figure 4). In this model, for the 8-bit representation, the electrical signal defining the brightness of each of the three primary colors can have one of 256 levels (from 0 to 255). This means that 16,777,216 colors can be defined in the model. The compromising emanations produced by the information display devices allow reconstruction of the data presented in them in the form of grayscale images [3; 4; 5; 6]. Due to the very low levels of the measured signals, the accompanying noise and environmental disturbances, the reproduced images are of poor quality [7; 8; 9; 10]. Very often it prevents data reading and analysis. However, these images may be subject to further processing, which allows us to obtain more information from the images by highlighting certain features [8; 11; 12; 13], for this purpose, e.g., algorithms of coherent summation, edge detection, context filtering [14; 15; 16; 17]. In each case, the obtained improvement in image quality enables easier perception of the data contained therein. However, this improvement is not always sufficient. In addition, it should be noted that the application of the above-mentioned image quality improvement algorithms still results in grayscale images or, in extreme cases (thresholding the pixel amplitude values), monochrome images.