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imcontrast

Adjust Contrast tool

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Syntax

imcontrast
imcontrast(h)
hTool = imcontrast(___)

Description

Use the imcontrast function to create an Adjust Contrast tool. The Adjust Contrast tool enables you to interactively adjust the contrast and brightness of a displayed grayscale image. For more information about using the tool, see Tips.

Adjust Contrast tool with sliders and editable fields that enable you to adjust the histogram of pixel values.

Note

The Adjust Contrast tool adjusts the values of the pixels used to display the image but does not change the actual image data. If you want to change the image data, use the imadjust function.

example

imcontrast creates an Adjust Contrast tool in a separate figure that is associated with the grayscale image in the current figure.

example

imcontrast(h) creates an Adjust Contrast tool associated with the image in the graphics container h.

hTool = imcontrast(___) returns the figure hTool containing the Adjust Contrast tool.

Examples

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Display an image and adjust the contrast of the image.

imshow("pout.tif")
imcontrast

Read an image into the workspace and define the handle of the figure as 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 imcontrast.

h1 = figure;
imshow("pout.tif")
h2 = figure;
imshow("coins.png")
imcontrast(h1)

Input Arguments

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Graphics object containing the image, specified as a Figure, Panel, Axes, or Image object. If h is an axes or figure, then imcontrast uses the first image returned by findobj(h,Type="image").

Output Arguments

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Adjust Contrast tool, returned as a Figure object.

Tips

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 pixel value less than the minimum, display 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, display 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.

  • Click and drag the mouse within the target image to interactively change the window values. Dragging the mouse horizontally from left to right changes the window width. Dragging the mouse vertically up and down changes the window center. 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.

  • 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.

  • The Adjust Contrast tool can handle grayscale images of class double and single with data ranges beyond the default display range of [0, 1]. For these images, imcontrast sets the histogram limits to fit the image data range, with padding at the upper and lower bounds.

Version History

Introduced before R2006a

See Also

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