We propose a method for automatically enhancing the eyes of all the faces in a digital image by whitening
their scleras (i.e., the white part of their eyes). The scleras are identified by combining existing face detection
and feature alignment technology with a color-based sclera probability map. We then smooth, brighten, and
desaturate the scleras. This reduces the appearance of blood vessels and produces a healthier, more "refreshed"
look.
The hybrid screen is a halftoning method that generates stochastic dispersed dot textures in highlights and
periodic clustered dot textures in midtones. Each tone level is sequentially designed from highlight to midtone
by applying an iterative halftoning algorithm such as direct binary search (DBS). By allowing random seeding
and swap-only DBS in a predefined core region within each microcell, we design each level while satisfying
the stacking constraint and guaranteeing a smooth transition between different levels. This paper focuses on a
number of enhancements to the original hybrid screen and their impacts on print quality. These include analytical
determination of the human visual system filter in the spatial domain for DBS, multilevel screen design either by
extending a bilevel screen or by directly generating a multilevel screen on the high resolution grid. Our results
show that the multilevel screen design method has a direct impact on hybrid screen design parameters such as
the optimal core size. We also extend the whole design process to color by jointly optimizing the color screens
using color DBS. Our results demonstrate a significant improvement in the highlights over halftones generated
by independently designed screen.
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