NWE Help: Graphics: XV: Selection

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Clicking and dragging the Left button of the mouse inside the image window will allow you to draw a selection rectangle on the image. If you're unhappy with the one you've drawn, simply click the Left button and draw another. If you'd like the rectangle to go away altogether, click the Left button and release it without moving the mouse.

Double-clicking the Left button inside the image window will create a selection rectangle the size of the currently displayed area of the image, or remove the previous selection as appropriate.

Once a selection rectangle has been drawn, it can be fine-tuned by clicking and dragging any of the handles that appear on its edge. If you press the < Shift > key while dragging a handle, the selection rectangle is kept square. If you press the < Ctrl > key while dragging a handle, the selection rectangle maintains the same aspect ratio it originally had.

You can move the selection rectangle by Left-clicking inside it and dragging it around. Pressing the < Shift > key while doing so will constrain the motion to the horizontal and vertical axes.

You can determine how large the selection rectangle is (in image coordinates) by bringing up the XV info window. Do this selecting Image Info from the Windows menu XV controls window or by pressing the i key inside any open XV window.

The XV info window will display, among other things, the current size and position of the selection rectangle in terms of image coordinates. For example, if it says:

114x77 rectangle starting at 119,58

it means that the current selection rectangle is 114 image pixels wide, 77 image pixels high, and that its top-left corner is located 119 image pixels in from the left edge of the image, and 58 image pixels in from the top edge. These values will be updated as you drag the cropping rectangle around.

If you want to set the size or position of the selection rectangle precisely, you can use the arrow keys on your keyboard. First, make the XV info window visible as described above. Second, use the mouse to draw a rough approximation of the selection rectangle that you want. You can now use the arrow keys to move the selection rectangle around the image. Once you've gotten the top and left sides of the selection rectangle precisely where you want them, you can move the bottom-right corner of the selection rectangle by holding the <shift> key down while using the arrow keys. Pressing the up arrow will make the rectangle shorter, and pressing the down arrow will make the rectangle taller.