Zavitz Elizabeth, Baker Curtis L
McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
J Vis. 2014 Jan 1;14(4):14. doi: 10.1167/14.4.14.
Lower order image statistics, which can be described by an image's Fourier energy content, enable segmentation when they are different on either side of a boundary. We have previously demonstrated that the spatial distribution of the energy in an image (described by its higher order statistics or structure) could influence segmentation thresholds for contrast- and orientation-defined boundaries, even though it was the same on either side of the boundary and thus task irrelevant (Zavitz & Baker, 2013). Here we examined whether higher order statistics can also enable segmentation when boundaries are defined by differences in structure or density of texture elements. We used micropattern-based naturalistic synthetic textures to manipulate the sparseness, global phase alignment, and local phase alignment of carrier textures and measured segmentation thresholds based on forced-choice judgments of boundary orientation. We found that both global phase structure and sparseness, but not local phase alignment, enable segmentation and that local structure also has a small effect on segmentation thresholds in both cases. Simulations of a two-stage filter model with a compressive intermediate nonlinearity can reproduce the major features of the experimental data, segmenting boundaries defined by higher order statistics alone while capturing the influence of global image structure on segmentation thresholds.
低阶图像统计量可通过图像的傅里叶能量含量来描述，当它们在边界两侧不同时，就能实现分割。我们之前已经证明，图像中能量的空间分布（由其高阶统计量或结构描述）会影响对比度和方向定义边界的分割阈值，即便在边界两侧是相同的，因此与任务无关（扎维茨和贝克，2013年）。在此，我们研究了在边界由纹理元素的结构或密度差异定义时，高阶统计量是否也能实现分割。我们使用基于微图案的自然主义合成纹理来操控载波纹理的稀疏度、全局相位对齐和局部相位对齐，并基于对边界方向的强制选择判断来测量分割阈值。我们发现，全局相位结构和稀疏度都能实现分割，但局部相位对齐不能，并且在这两种情况下局部结构对分割阈值也有微小影响。具有压缩中间非线性的两阶段滤波器模型的模拟可以重现实验数据的主要特征，仅根据高阶统计量定义的边界进行分割，同时捕捉全局图像结构对分割阈值的影响。
