Study on Image Graying Method for Defect Detection of Area Elements in Map Printing

In order to realize the automation of quality inspection in map printing, the development of quality inspection system based on machine vision is the dominant solution. Combining with the characteristics of map printing, the reason why it is difficult to identify the defects of light-colored area elements in the existing mainstream detection products was analyzed. It is mainly the color characteristics of map printing paper that causes the failure of the general grayscale algorithm. In this study, the image of printed matter to be detected was collected and the grayscale information of the image was obtained. The difference of grayscale between the area elements and the paper background in each channel of RGB was compared, and then the weights of each channel were defined to enhance the contrast between the defects of area elements and the paper background in the grayed image. The improved method was tested and verified in actual production. The experimental results showed that the improved weighted graying algorithm can effectively solve the problem that the low-saturation area elements cannot be recognized by the defect detection algorithms, which improved the efficiency of the whole map quality detection and proved the superiority of the solution.