Figure 6.96: Zoom.
See also: Menu Visualization ▹ Zoom Window.
The zoom window enables the interactive inspection of image details. You can open up any number of zoom windows with different zoom levels (see Menu Visualization ▹ New Zoom Window). The window also displays the gray values of each image channel at the mouse cursor position. Apart from this, the pixel type, the number of channels, and the current position of the mouse cursor are displayed. The percental scale can be selected from the combo box. It is related to the original size of the image.
There are multiple methods to navigate the zoom window:
Check Follow Mouse and move the mouse pointer over the image to select the zoomed area. Click once to keep the currently displayed area in the zoom window, when the mouse cursor moves out of the image window. Or, uncheck Follow Mouse and click (or drag) inside the image to select the zoomed area. The red square in the center of the zoom window indicates the position of the mouse cursor. The corresponding coordinates are also displayed at the bottom of the window.
You can select a particular pixel by clicking it. The zooming tool stores this position internally, and will redisplay the thus selected part of the image object when you leave the graphics window. This enables you to have a meaningful display in the zooming tool whenever you want to do actions outside of the graphics window.
For finer control of the zoomed area, click inside the zoom window to give it the focus and use the cursor keys to move pixel-wise. Press and hold the Alt key and use the cursor keys to move ten pixels at a time. Click inside the zoom window to move relative to the center position. For example, clicking ten pixels above the center will move the view up ten pixels.
The lower part of the window contains a gauge to display the gray value of the center pixel graphically. The range goes from 0 (left) to 255 (right). Normally, the gray value of the first channel is displayed with a black bar. For images with multiple channels the gauge is split accordingly to show individual bars for each channel. Thus, for color images in RGB-space (three channels with red, green, and blue values) three colored bars are used. If the gray value is below 1, the gauge is light gray (background). If the value is above 255, the gauge is dark gray or colored for RGB images.
Above the gauge, the gray values are displayed as numbers. Up to five channels are displayed. If more than five channels are present, the remaining channel values are truncated.
Next to the gauge, the coordinates of the mouse position are displayed. Below these, the image size, pixel type, and the number of channels are shown.