PCTFUS

Description

PCTFUS creates an output RGB color image by fusing a pseudocolor image with an input black-and-white intensity image, using the IHS transform (Cylinder or Hexcone model) or the Brovey transform.

Parameters

Name	Type	Caption	Length	Value range
FILE1 *	String	Input file name 1	1 - 192
DBIC *	Integer	Input pseudocolor image channel	1 - 1
DBPCT *	Integer	Pseudocolor table segment	1 - 1
FILE2 *	String	Input file name 2	1 - 192
DBINT *	Integer	Input intensity channel	1 - 1
DBINTLUT	Integer	Intensity lookup table segment	0 - 1
FILO *	String	Output file name	1 - 192
DBOC	Integer	Output raster channels	0 - 3
RESAMPLE *	String	Resample mode	4 - 8	Default: NEAR
FUSMODEL *	String	Fusion model	6 - 8	Default: CYLINDER
MONITOR	String	Monitor mode	0 - 3	ON, OFF Default: ON

* Required parameter

Parameter descriptions

FILE1

Specifies name of the image file containing one pseudocolor input channel, used to define the color (hue and saturation) component of the fused output image.

FILE1 and FILE2 must be in the same georeferencing units.

DBIC

Specifies the input pseudocolor image channel.

Exactly one channel must be specified. 16-bit or 32-bit values are linearly scaled to 8-bit values between 0 and 255 before applying the pseudocolor table.

Ranges of channels or segments can be specified with negative values. For example, {1,-4,10} is internally expanded to {1,2,3,4,10}. When you are not specifying a range in this way, only 48 numbers can be specified explicitly.

DBPCT

Specifies the pseudocolor table segment used for encoding the input image into red, green, and blue values.

FILE2

Specifies the name of the input file that contains the input intensity image for data fusion.

The files specified by FILE1 and FILE2 must be in the same georeferencing units.

DBINT

Specifies the input black-and-white intensity image that defines the intensity component of the fused output color image

DBINT (InputIntensity) must not be the same as DBOC (Output).

16-bit or 32-bit values are linearly scaled to 8-bit values between 0 and 255 before applying the lookup table.

DBINTLUT

Specifies a lookup table segment for enhancing the intensity input channel specified by DBINT (InputIntensity).

If this parameter is not specified, the intensity channel is not enhanced.

FILO

Specifies the name of the output file that contains three output color channels (DBOC) resulting from the data fusion.

FILE1, FILE2, and FILO can specify the same files. If the specified output file does not exist, a new file is created using the georeferencing bounds and minimum pixel resolution from FILE1 and FILE2.

DBOC

Specifies three output RGB channels to store the results of the data fusion.

DBIC (InputColor) defines the color, and DBINT (InputIntensity) defines the intensity for the fused output color image.

DBOC must be specified if the file specified by FILO exists. DBOC defaults to 1, 2, and 3 if the file specified by FILO does not exist.

The specified output channel must not be the same as the specified intensity channel. Duplicate output channels are not allowed.

Results are always 8-bit values between 0 and 255.

RESAMPLE

Specifies the type of resampling method used on both input images.

Resampling extracts and interpolates the gray levels from the original pixel locations to corrected locations.

The default resampling method is NEAR (NEAREST).

FUSMODEL

See the 'Details" and 'Algorithm' sections for more information about these fusion models.

MONITOR

The program progress can be monitored by printing the percentage of processing completed. A system parameter, MONITOR, controls this activity.

Available options are:

• ON: Turns the monitor ON (default)
• OFF: Turns the monitor OFF (recommended if running in batch or background mode)

Details

PCTFUS performs data fusion of an input pseudocolor image with a black-and-white intensity image using one of three fusion models: Cylinder, Hexcone, or Brovey.

The Hexcone model is used by many commercial image processing software products. The Hexcone model runs about 15 percent faster than the Cylinder model.

The Brovey transform is a highly effective transformation that generates a better looking image than the normal RGB image for many types of data, in particular for combining Landsat TM and SPOT Pan imagery. The Brovey transform is a formula-based process that is based on the band to display in a given color, the sum of all the color layers, and the intensity layer.

If FILE1 and FILO are the same and FILE2 is different, the black-and-white intensity image (DBINT) is resampled using the specified resampling method (RESAMPLE).

If FILE2 and FILO are the same and FILE1 is different, the pseudocolor input image is resampled using the specified resampling method (RESAMPLE).

If the output file does not exist, the new file is created with the georeferencing bounds of the input files and with the higher resolution of the two of them.

The lower resolution image is resampled using the specified resampling method.

If the output file (FILO) exists and it is different from those specified by FILE1 and FILE2, both FILE1 and FILE2 files are resampled to the FILO resolution using the specified resampling method (RESAMPLE).

The three input channels specified by DBIC (InputColor) represent the red, green, and blue channels, in that order. If one input channel is specified, the PCT segment must be specified. The three output channels specified by DBOC (Output) are used for the output of red, green, and blue, in that order.

FILE1, FILE2, and FILO (if it exists) must be in the same georeferencing units.

Examples

A USGS Land Use/Land Cover theme map on channel 6 of irvine.pix is fused with a 10-meter resolution panchromatic SPOT image in eltoro.pix. The result is a 10-meter resolution SPOT image with the land use classes overlaid in translucent colors.

Step 1: Add three 8-bit channels to eltoro.pix for storing the result.

EASI>FILE = "eltoro.pix"
EASI>PCIOP = "ADD"
EASI>PCIVAL = 3 ! add three 8-bit channels

EASI>RUN PCIMOD

Step 2: Enhance the input intensity image in eltoro.pix. Otherwise, the pseudocolor image colors overpower the intensity image.

EASI>FILE = "eltoro.pix"
EASI>DBIC = 1 ! use input channel 1
EASI>DBLUT = 2 ! use LUT segment 2
EASI>DBOC= 1 ! overwrite input channel
EASI>MASK=  ! process entire image

EASI>RUN LUT

Step 3: Use PCTFUS to fuse the data. Nearest neighbor resampling must be specified, because the input image is a theme map. In this case, the Hexcone model produces better results than the Cylinder model.

EASI>FILE1 = "irvine.pix"
EASI>DBIC = 6 ! use input channel 6
EASI>DBPCT = 7 ! use PCT segment 7
EASI>FILE2 = "irvine.pix"
EASI>DBINT = 1
EASI>DBOC = 2,3,4 ! use image channels 2,3,4
EASI>FILO = "eltoro.pix"
EASI>RESAMPLE = "NEAR"
EASI>FUSMODE = "HEXCONE"
EASI>MONITOR = "ON"

EASI>RUN PCTFUS

Algorithm

The equations used to convert Red, Green, and Blue color values to Intensity, Hue, and Saturation color values for both the Cylinder and the Hexcone IHS models are described in the 'Algorithm' section of the RGB and IHS documentation.

The Brovey transformation is a formula-based process that works by dividing the band to display in a given color by the sum of all the color layers (for example, Red, Green, and Blue) and then multiplying by the intensity layer (for example, SPOT Panchromatic layer).

R = Red, G = Green, B = Blue , I = Intensity (Panchromatic)

Red layer:

(R / (R + G + B)) * I

Green layer:

(G / (R + G + B)) * I

Blue layer:

(B / (R + G + B)) * I