All-in-Focused Image Combination in the Frequency Domain Using Light Field Images

Abstract

All-in-focused image combination is a fusion technique used to acquire related data from a set of focused images at different depth levels, which suggests that one can determine objects in the foreground and background regions. When attempting to reconstruct an all-in-focused image, we need to identify in-focused regions from multiple input images captured with different focal lengths. This paper presents a new method to find and fuse the in-focused regions of the different focal stack images. After we apply the two-dimensional discrete cosine transform (DCT) to transform the focal stack images into the frequency domain, we utilize the sum of the updated modified Laplacian (SUML), enhancement of the SUML, and harmonic mean (HM) for calculating in-focused regions of the stack images. After fusing all the in-focused information, we transform the result back by using the inverse DCT. Hence, the out-focused parts are removed. Finally, we combine all the in-focused image regions and reconstruct the all-in-focused image.

Refocusing Metric of Light Field Image Using Region-Adaptive Multi-Scale Focus Measure

“…A higher focus level indicates that the pixel has the better focus. The focus level of a pixel 𝐼(𝑥, 𝑦), denoted by 𝐹(𝑥, 𝑦), can be measured by a selected focus measure operator 𝐹𝑀 [9,18].…”

“…To demonstrate advantages of the proposed RA-MSFM, we render an all-in-focus (AIF) image using the proposed RA-MSFM. For performance comparison, AIF images using other state of art methods [15,17,18] are also generated.…”

“…The general refocusing capability of an LF image can be thought as the overall degree of focusing in the images refocused at arbitrary points. There has been research on focus measurement, however, it should be noted that most focus measures [10,11,12,13,14] were only developed with general 2D images in mind, thus there are only a few studies [15,16,18] that have looked at refocusing metric of light field images. The motivation and contribution of this paper is to design a measure of general refocusing capability of light field images.…”

“…Focus measures (FM) are widely used for many problems of image processing and computer vision, such as for depth from focus [15,16,20], autofocus [18], and so on.…”

“…This metric is used to evaluate compression loss by counting the in-focus pixels. Chantara [18] proposed a FM based on the Summation of the Modified Laplacian. This FM is used to select the focus area of an LF focal stack.…”