Application of digital color image analysis for colorimetric quality evaluation of surface defects on paint coatings

A method for the quality management of paint producers was developed that allows for an objective description of inhomogeneous fading of paint coatings after free weathering using relevant metric quantities such as color contrast, gradient of color contrast, and geometric features of the inhomogeneous structures. These may be quantified with the method of digital color image analysis. The first step to apply this technique means a systematic investigation of the color transformation properties specific of the selected input/output devices (CRT display, flatbed scanner) used for digital imaging. To build a color management system mathematical models of the color transformation processes were optimized and embedded in a commercial color image analysis software. The needed metric parameters, that evaluate the damages on the coated surfaces, must be deduced for highest possible agreement with visual judgements of experts on the categorization of the damages. 150 samples of paint coatings after weathering were selected to investigate this correlation.