Image colorization algorithm using series approximated sparse function

Abstract

This paper deals with an image colorization and proposes a new image colorization algorithm. Assuming that the difference of color values between neighbor pixels is given as a monotonically increasing function of the difference of grayscale values between neighbor pixels, a colorization function is proposed, and the colorization problem is formulated as the weighted least squares problem using this function. In order to reduce the dependence on the value of a parameter in the algorithm, this paper utilizes a finite series approximation and provides a fast colorization algorithm. Numerical examples show that the proposed algorithm colorizes a grayscale image efficiently.

Fast colorization based image coding algorithm using multiple resolution images

“…In order to provide a colorization-based image coding, this paper applies the colorization algorithm proposed in [4] because it can recover a full color image from a luminance image using only a few color pixels. The algorithm restores chrominance images C b and C r independently to obtain a color image, and this subsection gives a chrominance image restoration method.…”

“…The image colorization technique can recover a full-color image from a luminance image and several representative pixels (RPs) which have the chrominance values and their positions [1][2][3][4]. Levin et al proposes a well known colorization algorithm, which achieves a high colorization performance using appropriately given RPs.…”

“…In Section 2.2, we give a colorization algorithm based on the algorithm proposed in [4]. Section 2.3 proposes the RPs extraction algorithm which uses recovery error feedback, and it is applied to multiple resolution images.…”

“…Performance of the colorization algorithm affects the performance of the colorization-based image coding, that is, the colorization using a few color pixels leads to a high coding performance. To propose a fast and precise coding algorithm, this paper modifies the colorization algorithm proposed in [4] and introduces a multiple resolution scheme to reduce the computational cost. Figures 1 and 2 show the outline and concept of the proposed algorithm, respectively.…”

“…However, this algorithm requires high computing cost and fails to colorize a whole image if only a few RPs are given. The authors have proposed the colorization algorithm, which can restore a color image from only a few RPs and takes a low computational cost [4].…”