Development of the tecnique for digital colour specification and the new nomenclatures of ornamental rock based on the measured colours.

Abstract

This article introduces the method for quantitative digital colour specification for ornamental rock with help of scanner, showing its recent development. The digital image of polished dimension stone surface is scanned in true colour mode with optical resolution of 1,200 or 600 dpi. The captured image is submitted to moderation into 300 or 150 dpi in order to reduce pixel noise. The original software Wilbur analyses quantitatively pixel colour of the image, determining the chromaticity parameters, such as RGB, HSB and XYZ. The HSB system is adequate for quantitative classification of ornamental rock by its colour. At first, they are classified by S parameter (saturation), which represents colour vividness, into the following five categories: grey scale, S<4; slight colour, 4.013. In these categories, the greyscale rocks are sub-classified by B parameter (brightness) into 4 categories: black, B<25; dark grey, 2585. The middle and high colour rocks are sub-classified by H parameter (hue) into: red, 350