*Article* **PM2.5 Concentration Estimation Based on Image Processing Schemes and Simple Linear Regression**

**Jiun-Jian Liaw 1, Yung-Fa Huang 1, Cheng-Hsiung Hsieh 2,\*, Dung-Ching Lin <sup>1</sup> and Chin-Hsiang Luo <sup>3</sup>**


Received: 28 February 2020; Accepted: 23 April 2020; Published: 24 April 2020

**Abstract:** Fine aerosols with a diameter of less than 2.5 microns (PM2.5) have a significant negative impact on human health. However, their measurement devices or instruments are usually expensive and complicated operations are required, so a simple and effective way for measuring the PM2.5 concentration is needed. To relieve this problem, this paper attempts to provide an easy alternative approach to PM2.5 concentration estimation. The proposed approach is based on image processing schemes and a simple linear regression model. It uses images with a high and low PM2.5 concentration to obtain the difference between these images. The difference is applied to find the region with the greatest impact. The approach is described in two stages. First, a series of image processing schemes are employed to automatically select the region of interest (RoI) for PM2.5 concentration estimation. Through the selected RoI, a single feature is obtained. Second, by employing the single feature, a simple linear regression model is used and applied to PM2.5 concentration estimation. The proposed approach is verified by the real-world open data released by Taiwan's government. The proposed scheme is not expected to replace component analysis using physical or chemical techniques. We have tried to provide a cheaper and easier way to conduct PM2.5 estimation with an acceptable performance more efficiently. To achieve this, further work will be conducted and is summarized at the end of this paper.

**Keywords:** PM2.5 concentration estimation; digital image processing; automatic region of interest selection; data exclusion; linear regression
