calculate edge strength of image

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i am new to image processing and i need to calculate the strength of edge of a image.assume a situation you have same original image and you added blur effect to that image.the strength of edge of these two images are different.i need to calculate that edge strength for both images separately.so far i have get the canny edge detection of image using below code

Mat src1;

src1 = imread("D.PNG", CV_LOAD_IMAGE_COLOR);

namedWindow("Original image", CV_WINDOW_AUTOSIZE);

imshow("Original image", src1);

Mat gray, edge, draw;

cvtColor(src1, gray, CV_BGR2GRAY);

Canny(gray, edge, 50, 150, 3);

edge.convertTo(draw, CV_8U);

namedWindow("image", CV_WINDOW_AUTOSIZE);

imshow("image", draw);

waitKey(0);

return 0;

is there any method to calculate of the strength of this edge image..?