blend Documentation

blend - Apply polynomial correlation function to an image
BLEND will compute the overlapping areas of two input images and
determine a correlation polynomial function that will be applied to
the FROM image to histogram match the FROM2 image.

BLEND uses FIT and POLY to compute appropriate coefficients that when
applied to the TO file, the FROM file will be very close in tone to the
FROM2 file.  It can be thought of as a method of histogram matching.

Programmer: Kris Becker, USGS, Flagstaff, Az

File name of the cube
that is treated as X

NONE

Subcube specified for
FROM file

" "

Second input cube file
name.  Image will be
treated as the Y image

NONE

Subcube specified for
FROM2 file (Note: this
must select a single
band/image)

"::1"

Name of output file

NONE

Order of of polynomial fit

1

Title of the plot

"HISTOGRAM MATCHING"

Band/image number from the
FROM (input) file that will
be used to calculate the
correlation

1

Lowest value of valid DN

--

Highest value of valid DN

--

Minimum number points
that can be used to compute
correlation

5

Fractional minimum of total
points used to compute
correlation

0.0

Specifies the minimim
acceptable goodness of
fit/correlation between
the two images.  Correlation
range is 0 (worst) to 1
(best).

0.0

Specifies to use mapping
label information to determine
image overlaps

"YES"

ADDITIONAL NOTES:

Parm	Description
FROM	The name of the input cube file. This is the file that contains the image plane that is treated as the X image in the correlation function. (Default extention is .cub)
SFROM	The input subcube specifier. Allows the user to select a subarea of the input cube for processing. The default " " selects the entire cube.
FROM2	The name of the secondary input cube file. This file contains the image that will be used as the Y image in the correlation equation. (Default extention is .cub)
SFROM2	The secondary input subcube specifier. Allows the user to select a subarea of the second (FROM2) input cube for processing. This specifier must select a single band/image and the spatial dimensions of this input file must be equivalent to the input file (FROM). The default "::1" selects all LINES, SAMPLES and the FIRST band from this file.
TO	Specifies the name of the output cube file. This file will actually be the output of the "poly" program. See help on the poly program for additional information.
EQORDER	EQORDER is the order of the polynomial equation used. Valid values are 1-8.
TITLE	As each order of the correlation is computed a crude plot is generated. The value of this input paramter will be attached to the plot.
BAND	This parameter selects the BAND/image from the input cube file (FROM) that will be used to compute the pixel correlation.
LOW	The lowest value of valid DNs. If LOW = 11, then pixels with DN values 0-10 will be excluded from processing.
HIGH	The highest value of valid DNs. If HIGH = 200, then values greater that 200 will be excluded from processing.
MIN	Specifies the minimum number of points that can be used to compute the pixel registration. This value should be such that a least square fit function can return resonable results. Note that FRAC may also be used to give an additional option on specifying this value. Note, however, that BOTH MIN and FRAC cannot be used. If this case does occur, the value of MIN will be used.
FRAC	This parameter can also be used to specify a fractional miniumum of the total points that can be used to compute the pixel registration. For example, if FIT uses 2000 points maximum to compute the correlation and FRAC is 0.05, then the minimum number of points that can be used is MIN = (0.05 * 2000) = 100. Note, however, that BOTH MIN and FRAC cannot be used. If this case does occur, then the value of MIN is used.
GOODFIT	This parameter allows the user to specify a minimum acceptable goodness of fit. If the correlation bewteen the two images is less that GOODFIT, the no output file will be generated and the program returns an error condition. If the correlation coeeficient is greater than or equal to GOODNESS, then an output file will be generated using the returned pixel registration parameters. Note that the correlation coeeficient will range from 0 to 1 where 0 is the worst fit, 1 is the best fit. This parameter is very useful for simply testing correlation between two images. This can be easily achieved setting GOODFIT to any value greater than 1.0 (GOODFIT=2.0).
USEMAP	This parameter allows the caller to choose how the image overlap is determined. If USMAP="YES" (default), then BOTH FROM and FROM2 must have mapping parameters in the labels. These are then compared and used to determine overlapping image areas. Only overlapping areas are used to compute the fit. If the images do not have mapping information on the label or the user does not want to use them, set USEMAP="NO". For this case, the ALL lines and samples of both images are used to compute the fit. Thus the input subcube specifiers select the areas and they must match.