4.3.6.3 Histogram Normalization Tool
Histogram Normalization Tool Function:
The histogram normalization tool provides a mechanism to approximate
a piece-wise linear contrast stretch which will estimate a normalized
model histogram with a given mean and standard deviation.
The effect of setting the model parameters for mean and standard
deviation is to provide a method for controlling brightness and
contrast in a non-linear or normalized mode.
The fit of
the image histogram to the normalized model will vary depending on the
original image and therefore the manipulation will not set the image
mean and standard deviation exactly to the model parameters.
An additional parameter which specifies the step increment for the
piece-wise linear approximation can be varied to provide finer
grain control and better fit.
Automatic/On Apply radio buttons:
The Automatic mode applies the changes to the normalization controls
as each is being manipulated. The On Apply mode does not generate
the piece-wise linear approximation until the Apply button is pressed.
Mean slider:
The mean slider sets the mean for the model normalized histogram and
can be set to values from 0-255. Increasing the mean will brighten
the image while decreasing the mean will darken it.
Std. Dev. slider:
The Std. Dev. slider sets the standard deviation for the model
normalized histogram and can be set to values from 0-255.
Increasing the standard deviation will heighten the image contrast
while decreasing it lesses the contrast.
Step Increment slider:
The step increment slider set the size of the increment between
breakpoints for the piece-wise linear contrast stretch. The Step
Increment can be set from 1 to 255 and defaults to 10. Choosing a
smaller increment provides a finer-grain approximation with some
increased difficulty when utilizing the color tool for
adjument manually.
Apply button:
The apply button is used when the On Apply mode is set. The
button must be pressed in order to generate the piece-wise linear
approximation using the parameter values specified.
Dismiss:
The Dismiss button hides the histogram normalization tool window.