GetImageGradient code error

[zjd1988]

python code as follows:
Gradient is compute by AbsoluteMaximum

def AbsoluteMaximum(images):
assert(len(images) > 0)
output = images[0]
for i in range(1,len(images)):
output[np.abs(images[i]) > np.abs(output)] = images[i][np.abs(images[i]) > np.abs(output)]
return output

cpp code as follows:

std::pair<cv::Mat, cv::Mat> ARDepth::GetImageGradient(const cv::Mat& image){
....
cv::Mat img_grad_x = cv::max(cv::max(rgb_x[0], rgb_x[1]), rgb_x[2]);
cv::Mat img_grad_y = cv::max(cv::max(rgb_y[0], rgb_y[1]), rgb_y[2]);
....

cpp without abs operation