Colour matching for soft proofing using a camera

The goal of a colour management system (CMS) is to keep colour across different display devices. For example, a CMS may be developed to preserve colour from monitor to print. Printed colours on paper can look different from colours displayed on a monitor. Soft proofing is to preview a printed colour image on a monitor. The International Colour Consortium (ICC)/ColourSync media profile based on scanner and colorimetric devices are widely used to match between printed and displayed colours. This soft-proofing feature is effective only when accurate ICC profiles of monitor and printer are available with proper lighting condition. In this study, the authors present an on-site monitor-print colour-matching technique for soft proofing that uses a colour-measuring camera when appropriate device and illumination characteristics are not readily accessible. The proposed method consists of two matching steps: one is the estimation of lighting conditions and paper reflectance and the other is the estimation of printer and monitor characteristics. Lighting conditions and paper reflectance are measured by a camera using a white reference patch. Printer and monitor properties can be estimated using a number of colour samples in separate colour components (intensity and chromaticity). A three-dimensional look-up table method is used for intensity mapping, whereas chromatic adaptation is performed by a 2×5 transformation matrix and gamut mapping. Experimental results with several test images demonstrate that the proposed method shows better colour-matching performance, in terms of perceptual quality, than the soft proofing implemented in Photoshop.