Image Processing Toolbox User's Guide

Using the Window/Level Tool

The Adjust Contrast tool also lets you adjust contrast and brightness by clicking and dragging the mouse. In medical applications, this type of interactivity is often called adjusting the window/level.

When you start the Adjust Contrast tool and move the cursor over the image displayed in the Image Tool, the cursor changes shape to the Window/Level cursor . The following table summarizes the mouse motion.

Mouse Motion		Effect
Horizontally to the left		Shrinks the window from both sides
Horizontally to the right		Expands the window from both sides
Vertically up		Moves the window to the right over the histogram, increasing brightness.
Vertically down		Moves the window to the left over the image histogram, decreasing brightness.

The following example shows how to use the window/level capability to improve the contrast of an image.

1. Read an image from a sample DICOM file included with the toolbox.

• I = dicomread('CT-MONO2-16-ankle.dcm');
  

2. View the image data using the Image Tool. Because the image data is signed 16-bit data, this example uses the autoscaling syntax.

• imtool(I,'DisplayRange',[])
  
  
  

3. Start the Adjust Contrast tool by clicking the Adjust Contrast button in the Image Tool toolbar, or by selecting Adjust Contrast from the Tools menu in the Image Tool.
4. Move the cursor over the image. The cursor changes to the window/level shape .
5. Press and hold the left mouse button. As you move the window/level cursor horizontally to the left or right to adjust the contrast or move the cursor vertically up or down to change the brightness.

Adjusting Contrast and Brightness

Autoscaling

© 1994-2005 The MathWorks, Inc.