广 色 域 多 基 色 显 示 系 统 的 驱 动 图 像 生 成 方 法

Objective Wide-color-gamut display systems play an important role in the fields of electronic commerce, digital archives, design, simulation, and medical systems. In contrast to conventional three-primary display systems whose color gamut is limited to a triangle area, multi-primary display systems are more appropriate for wide-color-gamut display thanks to their larger polygonal color gamut. Nowadays, various multi-primary display systems have been put forward, such as four-primary, five-primary, and six-primary display systems. The theoretical studies of multi-primary display mainly focus on the conversion models between the multi-primary space and the standard CIE XYZ color space. However, the acquisition or production of driven images remains difficult for multi-primary display. It is a challenge for a conventional camera to capture color images which match multi-primary display with a wide color gamut. Besides, the driven images of multi-primary display have more than three channels, and thus they cannot be produced directly from three-primary images due to metamerism. In this paper, we introduce multi-primary LED dot matrix display, which has the advantages of a large size, a wide color gamut, high brightness, and a large dynamic range. To drive multi-primary LED dot matrix display with correct color reproduction, we propose a method to produce driven images for multi-primary display systems by using a conventional RGB camera. We hope that our method can be helpful for wide-color-gamut multi-primary display. Methods We measured the spectral sensitivity of four typical digital cameras, including Canon 1000D, Fuji X-E3, Nikon J1, and Sony F828, and analyzed their color acquisition ability. In light of the colorimetry theory and with numerical methods, we built a forward model which can convert the n-primary space of a display system to the standard CIE XYZ color space and then built an inverse model for the conversion from three-primary space to n-primary space by using a look-up table from three-dimensional space to n-dimensional space. A five-primary LED dot matrix display system was simulated utilizing typical LED components, and the ColorChecker SG target with a wide color gamut was used as the target image. We experimented with our conversion method on this five-primary LED dot matrix display system. Results and Discussions Since the target image is a raw color image of the ColorChecker SG target and its color gamut exceeds the sRGB gamut, it has the characteristics of a wide color gamut. If the illumination is changed, such as using a high-chroma light source, its color gamut can be further increased. When the colorimetric parameters of the five-primary LED dot matrix display are determined, the forward model can be easily built according to the proposed method. The chromatic aberration of 96 color blocks is mostly less than 2. Reducing the step size can lower the chromatic aberration of individual color blocks. The step-size parameter in the experiment is set as 25, which is the result of balancing the chromatic aberration and the calculation speed. The experimental results show that our method can produce images with the use of an RGB camera for driving the five-primary LED display system, and desired color reproduction can be achieved. There are some non-uniform distributions in the five-primary driven images, which will not affect the final display result. Conclusions The colorimetry theory and numerical methods help build a forward model and an inverse model for image conversion between the n-primary space of an LED dot matrix display system and the three-primary space of a CIE1931 XYZ system. The experimental results demonstrate that our models can easily produce multi-primary images from wide-color-gamut RGB images for driving LED dot matrix display and achieve desired color reproduction. Next, our work will focus on improvements in the color reproduction accuracy, the color gamut of the target image, the uniformity of the primary images, and the production speed of multi-primary images. It should be noted that our method is based on the assumption that the n-primary display system is in line with the principle of linear superposition, which is suitable for LED display systems. The method is promising in wide-color-gamut multi-primary display systems whose channels are highly independent.