Photoshop

Change a ruler’s zero origin

  1. (Optional) Choose View > Snap To, then choose any combination of options from the submenu. This snaps the ruler origin to guides, slices, or document bounds. You can also snap to the grid.
  2. Position the pointer over the intersection of the rulers in the upper left corner of the window, and drag diagonally down onto the image. A set of cross hairs appears, marking the new origin on the rulers.
    You can hold down Shift as you drag to make the ruler origin snap to the ruler ticks.

    To reset a ruler’s origin to its default value, double-click the upper left corner of the ruler.

    Dragging to create new ruler origin