POCS-based algorithm for restoring colour-quantised images

Abstract

The paper studies the restoration of colour-quantised images. Restoration of colourquantised images is rarely addressed in the literature, and direct applications of existing restoration techniques are generally inadequate to deal with this problem. The authors propose a POCS-based restoration algorithm specific to colour-quantised images, which makes a good use of the available colour palette to derive useful a priori information for restoration. The proposed restoration algorithm is shown to be capable of improving the quality of a colour-quantised image to a certain extent.

A simulated annealing restoration algorithm for restoring halftoned color-quantized images

“…All the aforementioned algorithms were originally proposed for handling noisy blurred color images. Fung's algorithm [16] adopts a POCSbased approach. Unlike [9][10][11], it was proposed for restoring color-quantized images.…”

“…Unlike [9][10][11], it was proposed for restoring color-quantized images. However, in [16], it is assumed that there is no halftoning involved in color quantization. Mese's algorithm [17] was originally proposed for inverse halftoning.…”

“…Observed Y Proposed Fung [16] Altunbasak-IND [11] Altunbasak-KL [11] Mese [17] Galatsanos [9] Hunt [10] Palette Mese's algorithm trains the linear prediction filter with best linear estimator [17]. In the training phase, the four standard images shown in Fig.…”

“…3 and their corresponding halftoned color-quantized outputs were used to train the filter. As for Fung's algorithm [16] and the proposed algorithm, no original fullcolor image is required to extract information and no training images are required to pre-train a linear prediction filter. Hence, additional credit should be added to the simulation results of these two algorithms.…”

Restoring halftoned color-quantized image with genetic algorithm

“…All these algorithms were originally proposed for handling noisy blurred color images. Fung's algorithm [17] adopts a POCS-based approach. Unlike [9], [10] and [II], it was proposed for restoring color-quantized images.…”