c++ - OpenCV HOGDescriptor 返回值

Question

为什么 HOG 描述符返回一个 float 而不是 int 的 vector ？它应该返回一个直方图..

Answer 1

根据这个 HoG note 来补充我认为正确的以前的答案我发现比最初的 Dalal & Triggs paper 更清楚，涉及两个归一化步骤:

• block 规范化

Group the cells into overlapping blocks of 2 x 2 cells each, so that each block has size 2C x 2C pixels. Two horizontally or vertically consecutive blocks overlap by two cells, that is, the block stride is C pixels. As a consequence, each internal cell is covered by four blocks. Concatenate the four cell histograms in each block into a single block feature b and normalize the block feature by its Euclidean norm.

• HOG 特征归一化

The final normalization makes the HOG feature independent of overall image contrast.

还应该在两个连续的 bin 之间进行双线性插值投票，以防止量化伪影。

此外，它不能是 int，因为您不仅要计算落入 bin 的梯度 vector 的数量，还要加上梯度幅度。