[CV] Computer Vision Features

Overview of LBP (codes)

The original LBP operator is defined as in a window of 3 ∗ 3, the center pixel of the window is used as the threshold, and the gray value of the adjacent 8 pixels is compared with it. If the surrounding pixel value is greater than or equal to the center pixel value, the pixel The position of the point is marked as 1, otherwise it is 0. In this way, 8 points in the 3 ∗ 3 neighborhood can be compared to generate 8-bit binary numbers (usually converted to decimal numbers, namely LBP codes, 256 types in total), that is, the LBP value of the center pixel of the window is obtained, and this value is used to reflect The texture information of the area. It should be noted that the LBP value is a binary number composed in a clockwise direction and has rotation invariance.

RLBP/DLBP/DRLBP

Their histogram calculation formula:




Reference: LBP-Based Edge-Texture Features for Object Recognition

Image derivative

The pixel values ​​of the image are all discrete, △x is generally taken as 1, then the
first derivative:

△f(x)=f(x+1)−f(x)