CROSSMOD -- Image Cross Correlation

Cross Correlate the 'original' image band with the 'reference' band to produce B0 and B1 coefficient matrices.

Normally the IMGFUSE script is used to automate the entire fusion process. The IMGLOCK procedure can be used to automate the entire image locking process.

PARAMETERS

CROSSMOD is controlled by the following global parameters:

Name     Prompt                                  Count     Type
FILI_ORG Input file (Original Image)             1-64      Char
FILI_REF Input file (Reference band)             1-64      Char
FILO     B0 and B1 Output file                   1-64      Char
DBIC_ORG Input channels from FILI_ORG            1         Int
DBIC_REF Input channels from FILI_REF            1         Int
DBOC_B0  Output channel for B0                   1         Int
DBOC_B1  Output channel for B1                   1         Int
MAXGAIN  Maximum model gain                      1         Real
KSIZE    Kernel size                             1         Int

FILI_ORG

Specifies the PCIDSK file that contains the image data to be locally modelled by the reference file. Both FILI_ORG and FILI_REF must be of the same dimensions.

 EASI>FILI_ORG = "original image filename"

FILI_REF

Specifies the PCIDSK file that contains the reference image data. Both FILI_ORG and FILI_REF must be of the same dimensions.

 EASI>FILI_REF = "reference filename"

FILO

Specifies the output PCIDSK file which will contain the B0 and B1 (8U) coefficient images.

 EASI>FILO = "Output image filename"

DBIC_ORG

Specifies the input channel from FILI_ORG - the original image. This should be an 8-bit unsigned image channel.

 EASI>DBIC_ORG = 1

DBIC_REF

Specifies the image channel to be used as the image reference in the algorithm. This should be an 8-bit unsigned image channel.

 EASI>DBIC_REF = 2

DBOC_B0

Specifies the image channel for the output b0 image. This should be 32-bit real image channel.

 EASI>DBOC_B0 = 3

DBOC_B1

Specifies the image channel for the output b1 image. This should be a 32-bit real image channel.

 EASI>DBOC_B1 = 4

MAXGAIN

Specifies the maximum model gain to be used for the modeling process.

 EASI>MAXGAIN = n                | MAXGAIN has a range of 0 to 256
 EASI>MAXGAIN =                  | defaults to 3

Lower values of MAXGAIN reduce the tendency of the algorithm to introduce noise into otherwise low texture or structured areas such as water regions. A typical starting point for MAXGAIN is 3. If there is resulting noise in the water regions, reduce this value. Reducing this value to less than 1 will result in blurred edges.

KSIZE

Specifies the size of the linear kernels over which the cross-correlation modelling is performed.

 EASI>KSIZE = 4
 EASI>KSIZE =                    | defaults to 7

Correlation is performed on a window of size ( 2 * KSIZE + 1 ) pixels. Sizes of less than 3 will produce noisier images. Sizes greater than 7 will blur edges.

DETAILS

CROSSMOD performs a cross correlation between the reference image (FILI_REF) and the original image (FILI_ORG). A horizontal and vertical kernel of KSIZE length is created. As this kernel scans across the window, the merit of both the horizontal and vertical kernels is evaluated. The correlation coefficients (b0 and b1) of the kernel with the best merit are then saved out to file (FILO).

When spatial enhancement is performed, the amount of detail from the reference image that will be fused into the ORIGINAL_OUTPUT image can be controlled using MAXGAIN; MAXGAIN sets the upper limit of the B1 coefficient of the kernel with the best merit. For example by setting MAXGAIN = 0, you will get the FILI_ORG as the output. There will be no spatial enhancement for that case.

EXAMPLE

In the multi-spectral image database ms.pix, cross model channel 3 (the original image) with channel 2 (the reference image), and place the output image into the first channel of b0.pix and b1.pix. Use a window width of 100 pixels, MAXGAIN of 3, and a kernel size of 7.

  EASI> FILI_ORG = "ms.pix"
  EASI> FILI_REF = "ms.pix"
  EASI> FILO = "b.pix"
  EASI> DBIC_ORG = 3
  EASI> DBIC_REF = 2
  EASI> DBOC_B0 = 1
  EASI> DBOC_B1 = 2
  EASI> MAXGAIN = 3
  EASI> KSIZE = 7
  EASI> RUN CROSSMOD

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