There are three types of color vision abnormalities: abnormal trichromatism, dichromatism and monochromatism. Normal color vision is three-component, and such color vision is called normal trichromatism. People with abnormal trichromatism need different quantitative ratios of primary colors. There are the following forms of abnormal trichromatism:
– protanomals (protanop) (Greek, protos – first);
– deuteranomals (deuteranop) (Greek, deuteros – second);
– tritanomals (tritanop) (Greek, trios – the third).
The protanomal has an insufficient amount of long wavelength L cones, so it is not sensitive enough to shades of red. Dalton himself suffered from this anomaly. According to the theory of Goering, they cannot be implemented red-green opponent mechanism, with the result that they are unable to distinguish between reddish and greenish shades.
In deuteranomals, sensitivity to green tones is reduced, which is a result of a lack of M cones; they also have difficulty distinguishing reddish from greenish tones. In tritanomals, there is a low sensitivity to violet tones characteristic of short-wave light, an insufficient number of S cones, less common than the rest. Tritanomals cannot distinguish between yellowish and bluish shades.
Figure 1.2.22 shows some test images for determining color vision anomalies. For people with normal color vision, various combinations of numbers and geometric shapes will be visible in the pictures [Abbasov, 2019].
People suffering from dichromatism need only two colors to reproduce all color tones, instead of three, like people with normal color vision. Monochromatism is also encountered – an extremely rare defect in color vision. To reproduce all the color tones of the spectrum, monochromes need only one primary color. People with such an anomaly of color vision can be called “color blind”; usually they do not see any colors at all.
Anatomically, the retina of the deuteranomals, protanomals and tritanomals differ from each other in the number of cones containing blue, green and red pigments. The cause of a defect in color vision is the relative lack of a specific cone pigment. Many people with color vision defects are not aware of this until a certain point. Some well-known artists also suffered from these anomalies (for example, Russian painter M. Vrubel with his gray-pearl scale; French artist, graphic artist S. Merion).
It should be noted that there is also the phenomenon of subjective colors. Under certain conditions, black and white stimuli can cause a sensation of color. Intermittent stimulation can cause neural processes that mimic the effects of colored stimuli.
Figure 1.2.22 Test images for determining color blindness.
Subjective Color Sensations
Experimental confirmation [Shiffman, 2008]. For 30 seconds, carefully examine the center of the rectangle with a diagonal pattern (Figure 1.2.23). You will begin to notice weak, unstable colored “streams” moving perpendicular to the black diagonal lines. Due to the micromovements of the eyeball, the image of the diagonals on the retina constantly moves, causing the rhythmic activity of the higher-level neurons of the visual system. Such patterns are not found in nature, so the visual system comes to an unstable state. This effect is most likely due to the fact that the size of the retinal projection of the structural parts of the image becomes co-measured with the size of the cone receptors themselves. In this case, the visual system goes into an unstable resonance mode, which causes illusions in the processing and perception of this visual information by the brain. Depending on the distance, the consequent retinal image size, this effect decreases or intensifies [Abbasov, 2016].
The work of [Doliotis et al., 2009] considers the phenomenology of colorblindness because up to 8-12% of men and 0.5% of women of European countries suffer from this abnormality of color sensation. Due to this, the necessity to work out the methods of modification of colored digital images to improve their perception by people with the defective vision has arisen. The particular data on the working out of methods of images modification for the color-blind people of the first category (protanopes that are insensitive to shades of red) are presented in the article. The colors causing the impairment of protanopes are assigned in the separate group, and the images are corrected and adapted for their perception [Itten, 2001]. The time of images processing is reduced due to the use of color quantization. This method but slightly changed may be also used for other types of color impairment. It may be applied to the deuteranopes who have some difficulty distinguishing shades of green.
Figure 1.2.23 Achromatic pattern that causes subjective color sensations.
Figure 1.2.24 Illustration based on dark shades of red and green and color illustration in the same shades of gray, color illustration, which in the gray version turns into a singlecolor image (horizontal strip) [Abbasov, 2013].
Figure 1.2.24, at the top shows an example of an illustration based on the dark shades of red and green. These shades are difficult to see (also for the author of the chapter), especially in a small area of the image. I would like to note that also these shades have the same tonality in the gray version. In the center for distraction, contrasting shades of blue, yellow and white are shown.
Figure 1.2.24, below, is a color illustration, which in the gray version turns into a single-color image (horizontal strip). This emphasizes the important role of color vision in human life. By the way, the color of the adjacent areas of the image is induced on this gray strip, although it is just gray [Abbasov, 2013].
1.3 Perception of Figures and Background
The work of [Buhmann et al., 1999] is dedicated to the methods of recognition of image and scenes in case of computer vision. Our visual system can reconstruct the three-dimensional figures on the basis of a flat image. The computer vision requires not only the recognition algorithms. Additionally, it is necessary to consider the lighting, shadows and scene perspective. Our perception of the surrounding world allows us to exclude the ambiguities. It is offered to apply the gestalt rules of objects grouping to recognize the scenes at the computer vision in the work. The images are to be analyzed from the whole to the part at the initial level while finding out the connection and interaction of constituent parts. Thereafter, the analyzed information is specified and interpreted. Furthermore, the objects are classified and recognized.
The visual field surrounding us consists
