| Summary: | 碩士 === 國立臺灣科技大學 === 色彩與照明科技研究所 === 107 === 3D printing is widespread in recent years. Color 3D printers are also available in the market now for rapid prototyping and small amount productions. However, evaluating the quality of 3D printing is an important but unresolved issue. The aim of this study is to evaluate color differences of 3D objects based on the HDR (High Dynamic Range) image. The experiment established a series of psychophysical experiments to evaluate the visual color differences. Observations includes entity viewing and image viewing. The image includes LDR (Low Dynamic Range) to HDR conversion. Multi-exposure LDR photos were integrated as HDR image using 3rd polynomial regression in logarithmic scales. In terms of color differences of 3D objects, simple and complex objects were tested psychophysically. The results were used to develop an imaging system for evaluating color differences of 3D objects.
The psychophysical experiment results show that the best LDR to HDR conversion method is to apply a knee function to adjust the tone of an LDR image. In the analysis of visual color differences, the results show that the 3D objects displayed in HDR mode can be closer to the real feeling compared to LDR mode. In the analysis of the monochromatic model, no matter which way to observe and evaluate the visual color differences, the weighting parameters of CIE94 and CIE2000 color difference formulae optimization result is approximately equal to (KL, KC, KH) = (2:1:1.5), which suggests that highlight and deep shadows are less important in the perceptual color differences. And the human eye would sense dark color difference easily. In the analysis of the multicolor model, the results indicate that the correct importance of the skin color of the human model. In terms of image differences, the results show that the perceptual color differences are well-correlated to 95th percentile of the image color differences.
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