MATCH

Description

Creates a lookup table that performs histogram matching of an input image to a master image. The output lookup table is saved to the input file and can be used by the function LUT to modify an input image.

Parameters

Name	Type	Length	Value range
Input: Image Layers: Input raster channel *	Raster port	1 - 1
Mask: Area mask	Bitmap port	0 - 4	Xoffset, Yoffset, Xsize, Ysize
InputMaster: Input master channel *	Raster port	1 - 1
MasterMask	Integer	0 - 4
Output: Lookup Table Layer: Output Lookup Table	LUT port	0 - 1
LUT Layer Name	String	0 - 1	Default: MATCH
LUT Layer Description	String	0 - 1
Tail Trimming % Left	Float	0 - 2
Tail Trimming % Right	Float	0 - 2

* Required parameter

Parameter descriptions

Input: Image Layers: Input raster channel

Specifies the input channel to match to the master image channel.

Mask: Area mask

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

InputMaster: Input master channel

Specifies the master image channel to be matched.

MasterMask

Specifies the bitmap layer that defines the area to be matched with the input raster. Only the pixels under the bitmap are processed; the rest of the image remains unchanged.

If no value is specified, the first quarter of the input image channel is processed.

Output: Lookup Table Layer: Output Lookup Table

Specifies the output LUT layer to which MATCH will write the new lookup table.

LUT Layer Name

Specifies a name (up to 8 characters) for the output LUT segment.

This string is displayed by ASL and may be changed using MAS.

LUT Layer Description

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

This string is displayed by ASL if LTYP is "SHORT" or "FULL", and may be changed using MAS.

Tail Trimming % Left

Specifies the percentage of tail trimming of the low end of the input histogram from the input and master image channels.

Tail Trimming sets a percentage of low-end non-zero points to zero; for example, if there are 1,000,000 pixels represented in a histogram and Tail Trimming is set to 0.01, the 1000 lowest pixel values are set to zero.

Tail Trimming % Right

Specifies the percentage of tail trimming of the high end of the input histogram from the input and master image channels.

Tail Trimming sets a percentage of high-end non-zero points to zero; for example, if there are 1,000,000 pixels represented in a histogram and Tail Trimming is set to 0.01, the 1000 highest pixel values are set to zero.

Details

MATCH produces a lookup table to match an input channel to a master channel. Image data on the input channel (Input) is read and matched to the master image channel (InputMaster).

The MASK and MCMASK (MasterMask) parameters specify areas of the input channel (MASK) and master channel (MCMASK) to use for matching.

If no value is specified, the entire channel is processed, and one quarter of the scanlines are used.

The output lookup table is stored in the input file (FILE). MATCH creates a new lookup table segment and stores the new segment's number in DBLUT (Output: Lookup Table Layer) before exiting. The segment name (DBSN) and descriptor (DBSD) for the new output lookup table may be specified. The LUT function can use the output lookup table to modify the input image.

A lookup table is generated to map the input histogram over the entire range of output gray level values. The low and high ends of the sample may be trimmed by specified percentages (TRIM) to eliminate outliers or noise.