Imshow vs mesh: Filter response flipped?

This is the same 2-D frequency response plotted using imshow and mesh. Why is the response flipped in imshow?

Using imshow:

Using mesh:

Answer 1

[Guillaume]

By convention for images the origin is the top left corner and the y axis points down. You can see that clearly if you make the axis visible after displaying your image:

imshow(yourimage);
axis on

[Sndn_Shr]

Thanks for the explanation! Is there a way to move the origin? to bottom-left and center?

[Guillaume]

As documented,

axis xy

to force the y axis to go up instead of down.