Adjust Contrast tool
htool = imcontrast(...)
imcontrast creates an Adjust Contrast tool in a separate
figure that is associated with the grayscale image in the current figure, called the
target image. The Adjust Contrast tool is an interactive contrast and brightness
adjustment tool, shown in the following figure, that you can use to adjust the
black-to-white mapping used to display the image. When you use the tool,
imcontrast adjusts the contrast of the displayed image by
modifying the axes
CLim property. To modify the actual pixel
values in the target image, click the Adjust Data button.
(This button is unavailable until you make a change to the contrast of the image.)
For more information about using the tool, see Tips.
The Adjust Contrast tool can handle grayscale images of class
single with data ranges
beyond the default display range, which is [0 1]. For these images,
imcontrast sets the histogram limits to fit the image
data range, with padding at the upper and lower bounds.
imcontrast( creates the Adjust
Contrast tool associated with the image specified by the handle
htool = imcontrast(...)
htool to the Adjust Contrast tool figure.
Read an image into the workspace. Adjust the contrast of the current image.
Read an image into the workspace and define the handle of the
h1. Open a second figure window and define the
handle of that figure as
h2. Adjust the contrast of the first
figure by specifying
h1 in the call to
h1 = figure; imshow('pout.tif'); h2 = figure; imshow('coins.png'); imcontrast(h1)
h— Handle to graphics object
Handle to a figure, axes, uipanel, or image graphics object, specified as
a handle. If
h is an axes or figure handle,
imcontrast uses the first image returned by
htool— Handle to Adjust Contrast tool figure
Handle to Adjust Contrast tool figure, returned as a handle.
The Adjust Contrast tool presents a scaled histogram of pixel values (overly represented pixel values are truncated for clarity). Dragging on the left red bar in the histogram display changes the minimum value. The minimum value (and any value less than the minimum) displays as black. Dragging on the right red bar in the histogram changes the maximum value. The maximum value (and any value greater than the maximum) displays as white. Values in between the red bars display as intermediate shades of gray.
Together the minimum and maximum values create a "window". Stretching the window reduces contrast. Shrinking the window increases contrast. Changing the center of the window changes the brightness of the image. It is possible to manually enter the minimum, maximum, width, and center values for the window. Changing one value automatically updates the other values and the image.
Clicking and dragging the mouse within the target image interactively changes the image's window values. Dragging the mouse horizontally from left to right changes the window width (i.e., contrast). Dragging the mouse vertically up and down changes the window center (i.e., brightness). Holding down the Ctrl key before clicking and dragging the mouse accelerates the rate of change; holding down the Shift key before clicking and dragging the mouse slows the rate of change. Keys must be pressed before clicking and dragging.