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ImageTools

  

Threshold

  

perform threshold operation on a grayscale image

 

Calling Sequence

Parameters

Options

Description

Examples

References

Calling Sequence

Threshold( img, thr, opts )

Parameters

img

-

Image; input image

thr

-

(optional) realcons; value of the threshold

opts

-

(optional) equation(s) of the form option = value; specify options for the Threshold command

Options

• 

low = float

  

Specifies the value that all pixels that fall below the threshold are set to.  The default value is 0.0.

• 

high = float

  

Specifies the value that all pixels that fall above the threshold are set to.  The default value is 1.0.

• 

method = above, below, or both

  

Specifies how the threshold operation is performed. Specifying method = above causes all the pixels that fall above the threshold to be set to the value specified by the high option, and the pixels that fall below the threshold retain their value. Specifying method = below causes all the pixels that fall below the threshold to be set to the value specified by the low option, and the pixels that fall above the threshold retain their value. Specifying method = both, which is the default value, causes all the pixels that fall below the threshold to be set to the value specified by the low option, and all the pixels that fall above the threshold to be set to the value specified by the high option.

Description

• 

The Threshold command performs a threshold operation on a grayscale image.

• 

The img parameter is the input image. It must be of type GrayImage.

• 

The optional thr parameter specifies the threshold. If not specified, a threshold is computed using Otsu's method.

• 

The effect of the threshold operation can be specified by the method option, by specifying whether to threshold pixels above the threshold, below the threshold, or both.

• 

The options high and low specify the new intensity values.

Examples

withImageTools:

imgMatrix200,200,y,x0.4sin0.05x+0.50.4sin0.1y+0.5+x1000,datatype=float8

_rtable18446884394278494326

(5.1)

Embedimg

img2_bThresholdimg,method=below

_rtable18446884394177715126

(5.2)

img2_aThresholdimg,method=above

_rtable18446884394177703558

(5.3)

img2Thresholdimg,method=both

_rtable18446884394177683814

(5.4)

Embedimg2_b,img2_a,img2

References

  

Otsu, N. "A threshold selection method from gray level histograms." IEEE Trans. Systems, Man and Cybernetics, Vol. 9. (1979).

See Also

GrayImage

ImageTools