图像区域不变矩的快速计算方法

Fast method for computing invariant moments within image regions

为了实时提取图像中任意尺寸窗口区域的不变矩,提出了一种快速计算方法。该算法通过构造一组积分图像,避免了在直接计算中出现的大量重复运算,使得图像中任一子窗口区域的不变矩都可以通过组合几个查找表运算得到。由于查找表运算的加法和乘法次数是恒定的,从而使得不同尺寸窗口区域的不变矩的计算均能在相同时间内完成。实验结果表明,该方法不会引起计算精度的损失,极大地降低了计算复杂度。对于从300×300pixels图像中提取的所有81×81pixels的窗口区域的不变矩这一任务而言,快速算法仅需31ms,比直接计算的速度提高了324倍。

To compute invariant moments within all arbitrary size window regions in an image in real-time, a fast method is proposed. By constructing a set of integral images, the method removes the large number of repeated computations presented in the direct method, and evaluates the moments of any window region conveniently through several table lookup operations. Since the number of table lookup operations is constant, then the moments for different window region sizes can he computed in constant time. Experimental results show that the fast method can provide the same accuracy as the direct one while decreases the computational cost significantly. Specifically, in an image with a resolution of 300× 300 pixels, the fast method requires only 31ms to extract all the moments for 81 × 81 pixels window regions, which is 324 times faster compared to the direct method.