Spectral Based Color Reproduction for E-commerce with High Compatibility

Recently, images of products are easily transferred to the customer in the E-commerce system, and are important information to decide to buy the products. The color of product is one of the important information. In this paper, spectral turn technique is proposed to achieve spectral based color reproduction in the e-commerce system with high lower compatibility to the conventional imaging technology. Introduction With the recent progress of broadband network such as ADSL, optical fiber, images of products are easily transferred to the customer, and are important information to decide to buy the products in the E-commerce system. This 21 century is thought as the age of 'personality' compared to the 'mass production' in the 20 century. In the E-commerce in this 21 century, people will hope to choose their favorite appearance of products. Color is one of the important factors of the favorite appearance. If the customer purchases a product in the e-commerce system, the product is physically send to the customer's office or home. Therefore, the customer can compare the color between original and reproduced color on display or hardcopy under the customer's environment. Device independent color reproduction based on ICC-profile[1] or sRGB color space[2] are used for color reproduction in recent technology. However, the accurate color reproduction is guaranteed on the decided environment. This is not practical for the use of general customer. Viewing condition independent color reproduction based on color appearance model is expected to reproduce the color under different viewing condition. In this reproduction, however, the reproduced appearance of color is that of color under taken illuminants. The color of the object under the customer's viewing condition can not be reproduced by this technique. Color reproduction techniques based on an estimation of reflectance spectra were proposed to reproduce correct color under an arbitrary environment [4-11]. The reflectance spectra are estimated from the multi-band images based on samples of reflectance spectra, which are measured previously. Using the estimated reflectance spectra and spectral characteristic of environmental illuminant, correct color is calculated and reproduced on a display or hardcopy by colorimetrical color reproduction. Spectral based color reproduction had been proposed by many group and researcher in these 15 years. However, they are not used practically in the E-commerce. We think that this is cased by following aspects. Since there are many resources and devices of conventional imaging technology, it is difficult to change them into those of spectral imaging technologies. In this paper, spectral turn technique is proposed to achieve spectral based color reproduction in the ecommerce system with high lower compatibility to the conventional imaging technology. Spectral Based Color Reproduction Total flow of spectral based color reproduction Figure 1 shows the total flow of spectral based color reproduction. The images of objects are captured under illuminant #1 by N-band camera. The obtained N-bands images are transformed into the spectral reflectance image. The spectral reflectance image is displayed or printed on various types of devices with consideration of viewing illuminant and color appearance transformations. In Figure 1, the color is reproduced on the conventional Figure 1 Flow of total process in spectral based color reproduction Figure 2 Process of spectral based processing for sRGB system primaries display, multi-primaries (more than four primaries) display, conventional hardcopy, spectral based hardcopy. From the next sub-sections, the details of spectral based color reproduction are described. Image Acquisition by N-band Camera and estimation of spectral reflectance The pixel value i m at the N-band camera in Figure 2 can be written as λ λ λ λ d L r s m nm