You may want to change an image’s zoom factor—either to view the complete image or to work on a specific detail. You can adjust the zoom in many ways; you access several methods directly from the Image window.

The zoom menu on the bottom bar of the Image window allows you to choose from among a few predefined zoom factors. You can also type in the desired factor directly.

Image: View > Zoom brings up another zoom menu, shown in Figure 10-21. Here you can choose among the same predefined zoom factors, plus two more. Note the keyboard shortcuts for common zoom factors. If you recently used a zoom factor that’s not predefined, it appears at the end of the menu.

You can also step up or down this scale using the ZOOM IN or ZOOM OUT entries. Note that the keys and also do this. Go back to the preceding zoom factor by using REVERT ZOOM or the key (backtick).

Figure 10-21. The Image: View > Zoom menu

Figure 10-22. Starting with a 50% zoom factor

The two remaining entries are best explained using examples. Figure 10-22 shows a window with a zoom factor of 50%. If we choose Image: View > Zoom > Fill Window, we get Figure 10-23. The zoom factor has been changed so the image fills the window’s dimensions. If we choose Image: View > Zoom > Fit Image in Window (or ), we get Figure 10-24. In this case, the zoom factor chosen gives the closest possible zoom while still keeping the full image visible in the window.

Note that all these zoom changes do not change the size of the window. On the other hand, the command Image: View > Shrink Wrap, or , changes the window size without changing the image’s zoom factor, in both single-window and multi-window mode.

Figure 10-23. After Fill Window

Figure 10-24. After Fit Image in Window

Figure 10-25. The Zoom tool icon

When pressing the key, you can use the mouse wheel to zoom in or out using the standard zoom factors.

If the small window resize button in the top-right corner of the Image window is checked, then changing the window size changes the zoom factor. This can be useful or irritating, depending on the situation.

Figure 10-26. Zooming in with the Zoom tool

Figure 10-27. After zooming in

Figure 10-28. The Zoom tool options

Figure 10-29. The Navigation dialog

Yet another tool is available for adjusting the zoom factor: the aptly named Zoom tool, which can be accessed from the Toolbox (Figure 10-25) or by pressing . Figure 10-26 shows this tool in zoom-in mode (as indicated by the + sign beside the mouse pointer). To zoom in, click and drag a rectangle around the part of the image you want to fill the window. Figure 10-27 shows the result.

This tool can also be used to zoom out. The rectangle you draw shows the new scale of the image after it’s zoomed out. Additionally, simply clicking the image with the Zoom tool zooms in or out along the zoom scale.

The Zoom tool has a few options, shown in Figure 10-28. You can zoom in or out or toggle this parameter by pressing the key. If you check the AUTO-RESIZE WINDOW checkbox, the window size changes so it contains the same part of the image as before.

If you still haven’t found the perfect zoom tool, here’s another one: Image: View > Navigation window. Choose this tool, and the small dockable dialog in Figure 10-29 pops up. The six buttons at the bottom provide the following functions:

The slider allows us to choose any zoom factor from 0.39% to 25600%. Finally, the image preview displays a frame around the part of the image that is currently displayed in the Image window. You can move it with the mouse pointer.