Selective Visual Attention: Computational Models and Applications

4.7 Amplitude Spectrum of Quaternion Fourier Transform (AQFT) Approach

Previous sections have introduced the bottom-up computational models of visual attention built based on the phase spectrum while setting the amplitude spectrum constant and keeping the phase spectrum. Actually, the amplitude spectrum of image patches in the whole image can also be used to build the computational model of visual attention for its representation of feature distributions for the image. In that case, the information of object locations is denoted by the saliency of image patches directly obtained in their frequency domain. This section introduces a computational model of visual attention built based on the amplitude spectrum of QFT [9]. In this model, the input image is firstly divided into small patches. Then the quaternion representation based on three features and QFT are obtained for each image patch. The amplitude spectrum of QFT of image patches is adopted to represent the colour, intensity and orientation distributions for these patches. The saliency value for each image patch is calculated not only by the differences between the QFT amplitude spectrum of this patch and other patches in the whole image, but also by the visual impacts for these differences determined by human visual sensitivity.

4.7.1 Saliency Value for Each Image Patch

In the proposed AQFT model [9], the saliency value of each image patch is determined by two factors: the patch's amplitude spectrum differences between an ...