The problem is that the 'image()' command doesn't scale your image, so the difference between 0 and 1 is very small and not properly displayed. If you use the 'imagesc()' command instead, your image will be automatically scaled and the edges will be visible. If you then want it in black-white instead of color you have to set the colormap accordingly, that is:
imagesc(CannyImage1);
colormap('gray')
Alternativly, if you have the image processing toolbox, you can use the 'imshow()' command instead, I find it better to use when working with images.