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ImageTools

  

Gamma

  

adjust gamma of an image

 

Calling Sequence

Parameters

Options

Description

Examples

Calling Sequence

Gamma( img, gamma, opts )

Parameters

img

-

Image; image to adjust

gamma

-

realcons; adjustment factor

opts

-

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

Options

• 

inplace = truefalse

  

Specifies whether the operation is performed in-place. This can be used to avoid allocating memory. The default is false.

• 

output = Image

  

Specifies a data structure into which the output is written. This can be used to avoid allocating memory. The size and number of layers must match that of the input. The dimensions of the output image are adjusted so that the row and column indices match the input. The default is NULL.

Description

• 

The Gamma command performs a gamma adjustment on an image and returns a new, adjusted image. Gamma is a measure of nonlinearity in the color intensities.

• 

The img parameter is the image to adjust.

• 

The gamma parameter specifies the adjustment.  Any numeric value is allowed, but typical adjustments are in the range 1/4 to 4. Values less than 1 lighten the midtones of the images, whereas values greater than 1 darken the midtones. The black (0.0) and white (1.0) levels are left unchanged.

• 

The correction is made to each color channel separately and is computed by raising each pixel's intensity value to the gamma power.

• 

If the image contains negative intensity values as a result of some previous image processing operation, gamma must be a positive integer. Otherwise, complex values will result and Gamma will return an error message. The Clip or FitIntensity commands can be used to ensure all intensity values are in the 0..1 range.

Examples

imagefilecatkerneloptsdatadir,/images/fjords.jpg:

withImageTools:

imgReadimagefile:

lighterGammaimg,0.7:

cannot_gammaimg0.1:

Gammacannot_gamma,0.7

Error, (in ImageTools:-Gamma) pixel values must be nonnegative with nonintegral exponent

dataCreate0.0,0.2,0.4,0.6,0.8,1.0:

printf%0.3f ,data

0.000 0.200 0.400 0.600 0.800 1.000

darker_dataGammadata,1.2:

printf%0.3f ,darker_data

0.000 0.145 0.333 0.542 0.765 1.000

See Also

ImageTools

ImageTools[Clip]

ImageTools[FitIntensity]

 


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