Fereshteh Abedini has successfully defended her thesis!

Image: Fereshteh Abedini presenting during her defence

Fereshteh Abedini has successfully defended her thesis!

We are very happy to announce that ApPEARS ESR Fereshteh Abedini has successfully defended her thesis titled ‘2D and 3D Halftoning for Appearance Reproductionat Linköping University on October 26, 2023. Congratulations, dr. Fereshteh Abedini!

Opponent: Dr. Jan Morovic, HP Inc.

Examination Committee: Professor Matilda Larsson, KTH; Professor Haibo Li, KTH; Professor Michael Felsberg, LiU.

The full thesis is available here and the abstract of her thesis is provided below.

Image: Print screen from the defence
Abstract of thesis

The appearance of an object is determined by its chromatic and geometric qualities in its surrounding environment using four optical parameters: color, gloss, translucency, and surface texture. Reconstructing the appearance of objects is of great importance in many applications, including creative industries, packaging, fine-art reproduction, medical simulation, and prosthesis-making. Printers are reproduction devices capable of replicating objects’ appearance in 2D and 3D forms. Accurate color reproduction is a critical quality measure in reproducing the desired appearance in any printing process. However, printers are devices with a limited number of inks that can either print a dot or leave it blank at a specific position on a substrate; hence, to reproduce different colors, optimal placement of the available inks is needed. Halftoning is a technique that deals with this challenge by generating a spatial distribution of the available inks that creates an illusion of the target color when viewed from a sufficiently large distance. Although halftoning has been used in 2D printing for many decades, it still requires improvements in reproducing fine details and structures of images. Moreover, the emergence of new technologies in 3D printing introduces a higher degree of freedom and more parameters to the field of appearance reproduction. Therefore, there is a critical need for extensive studies to revisit existing halftoning algorithms and develop novel approaches to produce high-quality prints that match the target appearance faithfully. This thesis aims at developing halftoning algorithms to improve appearance reproduction in 2D and 3D printing. Contributions of this thesis in the 2D domain is a dynamic sharpness-enhancing halftoning approach, which adaptively varies the local sharpness of the halftone image based on different textures in the original image for realistic appearance printing. The main contribution of this thesis in 3D printing is extending a high-quality 2D halftoning algorithm to the 3D domain. The proposed method is then integrated with a multi-layer printing approach, where ink is deposited at variable depths to improve the reproduction of tones and fine details. Another contribution of this thesis is studying the effect of halftoning on the perceived appearance of 3D printed surfaces. According to the results, changing the dot placement based on the elevation variation of the underlying geometry can potentially control the perception of the 3D printed appearances. The proposed methods in this thesis have been evaluated using different printing techniques.

Image: Fereshteh Abedini discussing with her opponent