To define a specific area, position the mouse pointer at a corner of the area; the pointer changes to a +. Hold down the mouse button as you drag the pointer across the image. When you release the mouse button, a rectangle on the screen identifies the scan area.
To adjust the size of your selected area, move the mouse pointer to the edge of the selection rectangle; the pointer changes to a double arrow. Hold down the mouse button and drag the edge of the rectangle to the new location.
You can also move the position of the selected area. Place the mouse pointer inside the selection rectangle; the pointer changes to a hand. Hold down the button to drag the selection rectangle to the new location.
Click the preview image to cancel the selection.
If your image is smaller than the document table, you can click the Auto Locate icon, 
, to select the entire image and crop out everything on the document table except the image. See “Using Automatic Features” in Chapter 4 for more information about using the Auto Locate icon.
Adjusting the source and target image sizes
The vertical and horizontal rulers along two sides of the preview window provide the measurements for the image you are previewing. You can change the unit of measure for these rulers by selecting inches, pixels, or cm (centimeters) from the Units
The size of the full image or the selected area appears in the Width and Height fields in the Source area. You can type new values in these fields to define a selection area of a specific size.