Zoom
After loading, the image is auto-scaled to fit to window size. You can change the image size using zoom commands.
Changing the zoom level
Rect Zooming 
, Zoom In, 
Zoom Out 
and Zoom Undo 
shortcut buttons are available on the toolbar.
| • | Rect Zooming - allows zoom by selecting rectangle on the image. |
| • | Zoom In (+) will enlarge the image. This action can also be performed with the [View > Zoom In] command. |
| • | Zoom Out (+) (or the [View > Zoom Out] command) will reduce the image. |
| • | Zoom Undo [Ctrl + U](or the [View > Zoom Undo] command will return the image to previous zoom, if it exists. |
Also you can use "+" key for zoom in and "-" key for zoom out.
Zoom selection
You can select a rectangular region of the image by clicking and dragging with the primary mouse button. After releasing the button, the image will be zoomed such as the selected area is fit to window size. Zoom can be canceled by pressing any key when the mouse button is pressed.
You can choose zoom value from zoom combo box 
in the toolbar, in percents accordingly to the original image's size.
The Fit drawing to window 
button commands ABViewer to shrink or to enlarge image to fit the ABViewer's window. Double-click on the mouse wheel executes the same action.
Using the mouse wheel
You can use mouse wheel for smooth changing the zoom level. In this case, the mouse cursor points to "base" point, which stays on the place when the zoom level is changed.