Fortunately there is a panner box in the upper right hand corner of the window which will show you the entire image with a bright green box indicating which subregion is displayed on the main part of the window. The advantage of this is that when you see a pixel, it is really a pixel, and you can easily evaluate things like bad pixels and columns. The disadvantage is that you cannot see the entire image at once, but must move the panner box in order to change the region being shown. A complete list of frame buffers is available by typing the command gdevices . Once the image is loaded, you can adjust the brightness and contrast parameters by moving the mouse in the window while holding down the right-hand button.
Higher contrast is achieved by moving the mouse vertically away from the center.
The most extreme displays are usually obtained when the mouse is in one of these two corners. You can learn the approximate pixel location of the mouse by reading the value in the box at lower right. The intensity is also displayed there. You may also zoom the picture using the middle mouse button. Press the button once and the image will move in an attempt to center up on the mouse cursor.