Nonsubsampled contourlet transform based tone mapping operator to optimize the dynamic range of diatom shells

Abstract

The diatoms have intricate silica-based cell walls with multi scale patterns. High Dynamic Range (HDR) imaging is widely used to examine the 3D structure of diatoms for recover ing the wide range of contrast and brightness. In order to construct a HDR image of a diatom, multiple images of the specimen are taken at different exposure settings with bright or dark field microscopy. In the proposed method, multi-scale decomposition (MSD) based on Nonsubsampled Contourlet Transform (NSCT) is adopted to separate the structured and detailed information of the HDR image. And then, by processing all layers independently, the tone mapped image is reconstructed to retain details present in the dark and light regions. Quantitative and qualitative analysis is performed in order to assess the performance of the pro posed and 7 existing Tone Mapping Operators (TMOs). In analysis, the study indicates that the proposed method en hances the diatom frustules to extract more details.