1.8 Zoom and New View

The functions Zoom and New View are for doing precision, pixel-scale work on an image. This section describes these particularly useful functions.

      
1.8.1 Zoom

Figure 1.16

  

Figure 1.16: Using Zoom

illustrates the use of Zoom. The Zoom function, enabled by clicking on the magnifying glass icon in the Toolbox, has two modes of operation. The first mode is used by clicking and dragging in the image window to frame a part of the image. When the mouse button is released, the delineated region is zoomed. Figure 1.16(a) shows a zoom selection area created with the mouse, and Figure 1.16(b) shows how this region is zoomed to fill the entire image window. This is a convenient way to zoom into a specific region of your image.

The second mode of operation for the Zoom tool is accessed by simply clicking or Shift-clicking in the image window. Each click zooms in a step and each Shift-click zooms out a step. The image window can also be zoomed in or out with keyboard shortcuts. Zooming in is performed by typing =  in the image window, and zooming out  is performed by typing - (that is, the minus key). Notice that the = is on the same key as the +, which should remind you that it adds or increases zoom. By contrast, the - key subtracts or decreases zoom. An advantage of the keyboard shortcuts is that they function without having to first click on the Zoom icon in the Toolbox.

The function Shrink Wrap,  found in the Image:View menu, can be used to resize the window to encompass the entire image, but only within the limits of your monitor's screen. Shrink Wrap can also be invoked by typing C-e in the image window.

Whenever a part of a zoomed image cannot be seen in the image window, the image panner, described in Section 1.1.2, can be used to pan to a desired image area. There are also three other possibilities for panning   in a zoomed image. There are the window's scroll bars, however, these probably aren't the most convenient method. The second choice is to middle-click and drag in the image window. This can work reasonably well if the image needs to be adjusted only incrementally. If it is necessary to pan back and forth between many different regions of a zoomed image, the Navigation Window   is probably the most convenient.

The use of the Navigation Window, found in the Image:View menu, is shown in Figure 1.17. Figure 1.17(a)

  

Figure 1.17: Using Zoom with the Navigation Window

illustrates an image zoomed to 200%, and Figure 1.17(b) shows the Navigation Window. This dialog allows the image to be panned in the image window by clicking and dragging on the view rectangle. You can also use the Navigation Window to control the degree of zoom by clicking on the + and - buttons.

        
1.8.2 New View

When performing detailed, pixel-scale operations on a zoomed image, it is useful to see what effect this is having on the image at normal scale, but it is inconvenient to zoom in and out after each operation. To solve this problem, there is the New View function, found in the Image:View menu. This function creates a new image window, which is a dependent view of the exact same image. Thus, operations performed in one window are also shown in the other. The Zoom function is the only exception to this and can affect one window without affecting the other. New View allows pixel-scale operations to be performed in one zoomed-in window while the same operations can be viewed in the other view window at normal scale.

Figure 1.18

  

Figure 1.18: Using New View

illustrates how the New View function works. Figure 1.18(a) shows a zoomed view of a pinecone, while Figure 1.18(b) shows a view of the same image with no zoom. As shown in Figure 1.18(a), red paint is being applied to a leaf of the pinecone with the Paintbrush tool. Figure 1.18(b) shows that the red paint is also visible in the unzoomed window. Note that the image and view numbers shown in the window title bars of Figures 1.18(a) and (b) are, respectively, 26.0 and 26.1. This indicates that these windows show views 0 and 1 of image 26.

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