Epson Expression 1680 Reference Manual page 34

Width (W) and height (H) values
The Source and Target width and height values are indicated in
the selected unit of measure. When the Preview window is open,
you change these values by typing new values in the fields and
pressing the Tab key, or by resizing the marquee, or frame,
surrounding a portion of the image in the Preview window. See
"Using Marquees" on page 2-30 for more information.
When the Preview window is closed, the Source values cannot be
adjusted, and you can only adjust the Target values by using the
Scale slider.
Units
Select pixels, inches, or cm as the unit of measure.
Storage size indicator
The storage size of an image is indicated in KB or MB. As you
change Target values, this value also changes.
2-14
Understanding EPSON TWAIN Pro Features