Fire Detection Algorithms Using Multimodal ... - Bilkent University

CHAPTER 2. FLAME DETECTION IN VISIBLE RANGE VIDEO 14output of the first step of the algorithm is a binary pixel map Blobs(x,n) thatindicates whether or not the pixel at location x in n − th frame is moving.Other more sophisticated methods, including the ones developed byBagci et al. [3] and Stauffer and Grimson [77], can also be used for movingpixel estimation. In our application, accurate detection of moving regions is notas critical as in other object tracking and estimation problems; we are mainlyconcerned with real-time detection of moving regions as an initial step in the fireand flame detection system. We choose to implement the method suggested byCollins et al. [19], because of its computational efficiency.2.2.2 Detection of Fire Colored PixelsColor values of moving pixels are compared with a pre-determined color distribution,which represents possible flame colors in video in RGB color space. Theflame color distribution is obtained from sample images containing flame regions.The cloud is represented by using mixture of Gaussians in the RGB color spaceas described in [69] and [77].Similar to the model in [77], the values of a particular pixel corresponding toa flame region is considered as a ‘flame pixel process’. The ‘flame pixel process’ isa time series of RGB vectors of pixels in a flame region. Let I(x, n) be a pixel atlocation x of the image frame at time step n with color values r I (x, n), g I (x, n),and b I (x, n) corresponding to red, green and blue channels. At any time step n,the history of the pixel vectors are known:{Q 1 , ..., Q n } = {[r I (x, m), g I (x, m), b I (x, m)] : 1 ≤ m ≤ n} (2.5)where Q m = [r I (x, m), g I (x, m), b I (x, m)], represents the RGB color vector forthe pixel at location x and time step m.A sample ‘flame pixel process’ is shown in Fig. 2.2 (a). It represents a flamecolor distribution in RGB color space corresponding to a particular fire. Differentcolor distributions and flame pixel processes can be obtained by observingdifferent types of fire depending on the burning material.