superimpose quiver plot onto image

Hi,

Does anyone know a way of superimposing the gradient vector field of an image onto the image itself? As far as I can tell, the "quiver" function should allow this, but I cannot get it to work... it just shows a blue figure. This is the code I am using:

img = imread('bubbles.jpg');

ycbcr = rgb2ycbcr(img);

lum = ycbcr(:,:,1);

[gx gy] = gradient(lum);

figure('name','Gradient');

imshow(dens,[],'InitialMagnification','fit');

hold on;

quiver(gx(1:r,1:c),gy(1:r,1:c));

title('Gradient Field');

Thanks for any help you are able to give me.

Answer 1

[Sulaymon Eshkabilov]

Here is the complete solution script:

img = imread('Bubble0.jpg');
GI = rgb2gray(img);
[gx, gy] = gradient(double(GI), .5, .5);
[r, c, LA]=size(img);
figure('name','Gradient');
imshow(img(1:r,1:c),'InitialMagnification','fit');
hold on;
quiver(gx(1:r,1:c),gy(1:r,1:c), 1);
title('Gradient Field');
figure
quiver(gx(1:r,1:c),gy(1:r,1:c), 10);
title('Gradient Field')