extract quiver magnitude of an image

The following code display the quiverplot.How can i get the magnitude of arrows in quiverplot??? I = imread('rice.png'); I=double(I); img_s = conv2(I,matrix,'valid'); [gx, gy] = gradient(img_s); imshow(gx, []); figure; imshow(gy, []); [x,y] = meshgrid(1:size(img_s,1),1:size(img_s,2)); quiver(x,y,gx,gy)

Answer 1

[Thorsten]

To double the length of the arrows:

quiver(x,y,2*gx,2*gy)