建構色彩分布密度理論以皮膚色為例

Abstract

一台顯示器是否能夠重現真實的色彩一直是人類想要知道的議題，於是提出了色彩分布指標(Color Distribution Index, CDI)，將色域內的體積切割成許多的切割單元，並且以單元內的色點有無來做評斷的標準，然後以位元深度、對比度、Gamma曲線進行分析。 但是因為Lu'v'表色系統有低亮度區域較不符合人眼對色彩的認知的關係，而L*a*b*表色系統相較於Lu'v'表色系統有更適合於人類的特性。所以後來修正色彩分布指標(modified Color Distribution Index, mCDI)將設定的表色系統更改為L*a*b*表色系統，並且也以位元深度、對比度、Gamma曲線進行分析。不過由於只定義格子內的點數有無使得在CDI及mCDI在分析時只會計算有色點的格子的比例，這讓在分析的時候會失去一些資訊。 於是本論文提出了密度的概念，利用密度的想法來重新定義色點在空間色域中的數值，並且結合資訊熵的概念將密度的統計結果做分析，然後將結果整合成一個新的數值，而且定義為色彩分布密度(Color Distribution Density, CDD)。最後將其應用於分析，然而對於消費者來講，有些人會對特定的顏色比較感興趣，所以本論文會以皮膚色做為一個範例來探討在特定色域下的顯示器評估。

People always want to understand whether the displays can reproduce the colors or not and then Color Distribution Index(CDI) was present. The volume in color space is cut into a lot of cells and judge whether color point is in the cell or not. After that, doing the analysis about different bit depth, contrast ratio and Gamma curve with CDI. Modified Color Distribution Index(mCDI) was proposed because Lu'v' color space is not applicable at low luminance and L*a*b* color space is more suitable for human's eyes. It used the concept of CDI on L*a*b* color space and also analyzed with different bit depth, contrast ratio and Gamma curve. However, CDI and mCDI only defined the exist of color point inside the cell and calculated the percentage of the cells which color points are in. It will lose some information in analysis. Consequently, we proposed the concept of density and redefined the value of color point in color space. Then, we combined the concept of Entropy to statistical analyze. Finally, we got a new value from results and named it Color Distribution Density(CDD). For some consumers, they have more interesting on certain color tone. So, we will study on skin tone for an example in this paper.