FUN

Description

FUN generates a lookup table (LUT) to perform a specified function and stores it in a database lookup table segment. Supported functions include histogram equalization, histogram normalization, histogram matching, infrequency brightening, and adaptive enhancement.

Parameters

Name	Type	Length	Value range
Enhancement Function *	String	2 - 1	EQUA | NORM | MATC | INFR | ADAP
Input Raster Layers: Input raster channel(s) *	Raster port	1 - 1024
Output LUT Layer: Output lookup table segment	LUT port	0 - 1024
LUT Layer Name	String	0 - 1
LUT Layer Description	String	0 - 1
Minimum Output Gray Level	Integer	0 - 2
Maximum Output Gray Level	Integer	0 - 2
Standard Deviations Per Tail	Float	0 - 1	Default: 3.0
Tail Trimming % Left	Float	0 - 2
Tail Trimming % Right	Float	0 - 2
Mask: Area mask	Bitmap port	0 - 4

* Required parameter

Parameter descriptions

Enhancement Function

Specifies the type of enhancement to perform.

Input Raster Layers: Input raster channel(s)

Specifies a set of input channels to be sampled for lookup table generation.

Duplicate channels are NOT allowed.

Output LUT Layer: Output lookup table segment

Specifies the LUT segment(s) in the input file to receive the generated lookup table.

The value of this parameter must be less than or equal to the number of input channels (DBIC). Duplicate segments are NOT allowed.

If the output LUT segment is explicitly specified, the existing lookup table segment is overwritten.

If this parameter is defaulted, a new lookup table segment is created. Upon completion, the parameter returns a list of segment numbers used to save each of the LUT segments written.

LUT Layer Name

Specifies a name (up to 8 characters) for the output segment, if a new one is created.

LUT Layer Description

Describes (in up to 64 characters) the contents or origins of the output LUT.

Minimum Output Gray Level

Specifies the minimum gray-level output to which the the output is mapped.

Maximum Output Gray Level

Specifies the maximum gray-level output to which the the output is mapped.

Standard Deviations Per Tail

Specifies the number of standard deviations to be included in each tail for the Histogram Normalization function.

This value is a real number, in units of standard deviations. The default value is 3.0.

Tail Trimming % Left

Specifies the percentage of tail trimming of the low end (left) of the input histogram(s).

Tail Trimming % Right

Specifies the percentage of tail trimming of the high end (right) of the input histogram(s).

Mask: Area mask

Specifies the bitmap that defines the area of the input raster to be processed.

This value represents the layer number of the bitmap segment in the input file. Only the pixels under the bitmap are processed; the rest of the image remains unchanged.

If no value is specified, the entire channel is processed.

Details

FUN generates a lookup table to perform a specified function and stores it in a database LUT segment.

FUN reads image data from a set of input channels (DBIC) and uses the histograms to generate lookup tables, which FUN then stores to a set of LUT segments (DBLUT) for later use by LUT or IVL. If the output LUT (DBLUT) is not specified, FUN creates a new LUT segment for each input channel specified, and stores the segment numbers in the output LUT segment. If new LUT segments are created, the segment name (DBSN) and a description (DBSD) may be defined. If the output LUT is specified, FUN overwrites the existing lookup table segments.

A lookup table is generated to map the input histogram over the entire range of output gray-level values. By default, the output range is 0 to 255, but the user may explicitly specify the minimum and maximum output gray levels (OSTR).

The MASK parameter specifies the area within the input channel to process. Only the area under the mask is read; the rest of the image is not used.

If MASK is not specified, the entire database is sampled and one quarter of the pixels in one quarter of the scanlines are used.

The low and high ends of the sampled area can be trimmed by specified percentages (TRIM) to eliminate outliers or noise.

Enhancement functions