A fast rotation histogram of gradients(RHG) feature descriptor is presented.Usually,to achieve rotation invariance,the main orientation of a feature descriptor is figured out,and then the coordinates of the sample region and the gradient orientations are rotated around the main orientation with low efficiency.The RHG descriptor can achieve rotation invariance by rotating the bins of its gradient histogram and avoid boundary effect by the combination of bins.The step of main orientation is also merged into t...