何时闭式RGB->S/P比是充分的？用于中间视觉显示的自然场景高光谱表征
When is a closed-form RGB->S/P ratio adequate? A hyperspectral characterization on natural scenes for mesopic display
AI总结：
该研究通过高光谱自然场景数据验证闭式RGB到S/P比映射的充分性，发现色适应至D65后误差显著降低，且对光谱平滑内容表现良好，但窄带光源不适用。
AI中文摘要：
中间视觉和低光显示变换需要逐像素的暗视-明视亮度比（S/P）作为驱动信号；对于普通RGB内容，精确的光谱S/P不可用，因此使用一种从线性RGB三元组估计S/P的低成本闭式形式来代替。此类闭式形式存在，但仅在窄带/LED光源（即光谱稀疏光谱）上进行了表征，其中三通道投影的相对误差约为41%。然而，显示内容是自然且宽带的。我们使用高光谱图像中的逐像素光谱S/P作为地面真值，探讨相同的闭式形式在那里是否充分。在日光辐射时间序列上，六标量闭式形式（三个明视和三个暗视通道权重）以约0.07的中位误差重现光谱S/P，且一旦RGB输入经色适应至D65，该误差随时间不变；在未适应的sRGB中评估时，误差反而随光源呈现色温倾斜（约0.19），因此适应是此用例的关键步骤。该结果推广到独立的五十场景集（合并中位数0.024；45/50场景在预登记的0.10范围内），少数超出集中在接近窄带机制的饱和、光谱峰值表面（该集中的花卉特写）。暗视权重向量被证明依赖于主模型，但此处使用的值通过无主模型XYZ投影得到证实，且在所有原则性系数选择下，中位误差保持在范围内。我们不声称观察者验证的外观保真度或窄带光源上的充分性；两者均不在范围内。两种结果均源于相同的三通道投影：它被光谱稀疏输入压倒，而在光谱平滑输入上则充分。
英文摘要：
Mesopic and low-light display transforms require, as their driving signal, a per-pixel scotopic-to-photopic luminance ratio (S/P); the exact spectral S/P is unavailable for ordinary RGB content, so a low-cost closed form that estimates S/P from a linear-RGB triplet is used in its place. Such closed forms exist but have been characterized only on narrowband / LED sources, i.e. spectrally sparse spectra, where a relative error of ~41% has been reported for a three-channel projection. Display content, however, is natural and broadband. We ask whether the same closed form is adequate there, using per-pixel spectral S/P from hyperspectral imagery as ground truth. On a daylight radiance time-series, a six-scalar closed form (three photopic and three scotopic channel weights) reproduces spectral S/P with a median error of ~0.07 that is time-invariant once the RGB input is chromatically adapted to D65; evaluated in un-adapted sRGB the error instead carries a color-temperature tilt across illuminants (~0.19), so adaptation is the enabling step for this use case. The result generalizes to an independent fifty-scene set (pooled median 0.024; 45/50 scenes within a pre-registered 0.10 band), with the few exceedances concentrated in saturated, spectrally-peaky surfaces that approach the narrowband regime (floral close-ups in this set). The scotopic weight vector is shown to be primary-model dependent, but the value used here is corroborated by a primary-free XYZ projection, and the median error stays within the band across all principled coefficient choices. We do not claim observer-validated appearance fidelity or adequacy on narrowband sources; both are out of scope. Both outcomes follow from the same three-channel projection: it is overwhelmed by spectrally sparse inputs and adequate on spectrally smooth ones.
