HistScaleImg

DESCRIPTION

Performs histogram scaling of an image. A certain specified percentage of the high intensity points is clipped to a specified clamp value. Similarly a certain specified percentage of the low intensity points is clipped to a specified clamp value. The intervening intensities are linearly scaled between the two specified clamp levels. This operation can be used to enhance the contrast of an image. Histogram scaling is discussed in:

Digital Image Processing, Gonzales, R.C., Wintz, P., Addison Wesley, Second Edition, 1987, pp 144--160.

INPUTS

Port: Img In
Type: Lattice
Constraints: 1..3-D
Source image.

WIDGETS

Port: High Out
Type: Dial
Percentage of high values to clip.

Port: Low Out
Type: Dial
Percentage of low values to clip.

Port: High Clip
Type: Slider
High clipping value.

Port: Low Clip
Type: Slider
Low clipping value.

OUTPUTS

Port: Img Out
Type: Lattice
Constraints: 1..3-D
Clipped and scaled image.

KNOWN PROBLEMS

When clipping 100% of the high values to a High Clip value of 255, some RGB byte images are not entirely clipped to white (all channels 255). In the observed case, the area not clipped is a few percent of the total image area.

SEE ALSO


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© The Numerical Algorithms Group Ltd, Oxford UK. 2000