# The Algorithms of Image Processing and Analysis in the Textile Fabrics Abrasion Assessment
## 4 Results
The protruding fibres made the fabric surface brighter, more pixels are indexed in higher values, which significantly varied the shape of brightness level density function. Therefore, the instrumental method of abrasion resistance assessment provided more precise, complex results for Fabric 2 in comparison with standard methods. Figure 5: Skewness graph–Fabric 2. The assessment of surface changes on Fabric 3's surface was realized until the number of rubs described in the standard [22] was reached. At the end of the test (51,200 rubs reached), the fabric surface did not vary significantly, only grade 1 (meaning a slight change in colour vividness) was obtained. The test, carried out using the instrumental method, enabled the identification of colour alterations and slight surface changes just at the beginning of the test. The skewness values, presented in Figure 6, went down or up (according to channel) after the first interval (1600 rubs), then fluctuated during the whole test. The skewness variations observed were generally connected with the slow, but sure, fading of samples and the loss of their initially shiny surfaces during the abrasion process. The lower the skewness measured for the channel *a histogram and the higher the skewness measured for channel *b, the less green and more yellow the colour of Fabric 3's surface became. In laboratory practice, the variation in the vividness of colour on the coated fabric's surface was evaluated subjectively. Implementation of the instrumental method provided the opportunity to more precisely identify surface changes (colour, shine) of the coated fabric. The next fabrics subjected to abrasion resistance analysis were cotton woven fabrics--Fabrics 4 to 6. The mentioned fabrics were divided by weaving pattern and technological parameters such a warp and weft density and mass per unit area. Fabrics 4 to 6 represented different abrasion resistance values, tested according to the standard [11], from 10,000 up to 25,000 rubs. The pilling phenomena occurred during the tests. Generally it was found that Fabrics 4 and 5 (plain and broken twill weaves had a prevalence of negative skewness values (Figures 7 and 9), which meant that the sample colour was getting redder (channel *a) and more yellow (channel *b). Despite not being dyed, the samples' surfaces showed some traces of colour, even if not visible to the human eye. Figure 6: Skewness graph—Fabric 3. For Fabric 4, the negative skewness values were obtained (Figure 7) for both image channels. Similar to previous graphs, skewness fluctuated, regarding changes on fabric surface such as the occurrence of loose, protruding fibres and pills of different shapes and sizes. At the end of the abrasion process (two threads broken at 10,000 rubs), the skewness for channel \"b reached positive values, the brightness level histogram moved to a more blue colour. The intense pilling occurred after 4000 rubs, which was a pivotal point in the process of the final damage of Fabric 4 (two separate threads were broken). The threads were getting thin, more single fibres were broken and pills had grown, destroying the surface structure. In the case of Fabric 5 (Figure 8), skewness showed negative values for channel \"a of the CIELAB image, which meant a shift of the brightness level histogram towards red. The skewness calculated for the second channel-\"b went up and down during the whole test, which was dependent on the pilling stages (from loose protruding fibres to formed pills), observed on Fabric 7's surface. The above mentioned skewness changes were not only seen in value but in the signs too. The longer the abrasion  
Figure 8: Skewness graph—Fabric 5. Figure 7: Skewness graph—Fabric 4.  
resistance test lasted, the more diverse the skewness values, especially for channel *b, until the end of the process. The skewness values calculated for Fabric 6 related to test duration (presented in number of rubs) are shown in Figure 9. The cotton satin woven fabric gave an oscillated skewness, but for channel *b only.