Help for DC


PURPOSE:

	"dc" is a VICAR applications program which will fit a straight line
to DN versus exposure at each pixel of several input frames and output a zero
exposure or "dark current" picture. DC will also optionally output a slope
picture, a predicted Y value picture and/or a file of deviated points from
the fitted line. This allows the spatial responsivity of linear detectors to
be evaluated with two or more output pictures.

EXECUTION:

"dc" can be executed by the following statement:

	dc INP=(IN1,IN2,...) OUT=(DC,SLOPE,YPOINT,DELTA) SIZE=(SL,SS,NL,NS) PARMS

where INP, OUT, SIZE, and PARMS are required or optional parameters for DC
and are explained in TUTOR mode under TAE.


	EXPO	'NEGATIVE    MAXDN     SCALE 
	X       CONS

The input images may either be (all) byte or (all) halfword data.  The data 
format is taken from the VICAR label of the first input file.  The output image
has the same data format (byte or halfword) as the input image. 
OPERATION:

     "dc" fits a straight line on a pixel by pixel basis on two to ten input
pictures in a light transfer sequence. DC extrapolates to zero exposure. If the
analyst suspects for some reason that the zero exposure picture would be
negative, has the option of outputting the negative of the zero exposure
picture. Figure 1 graphically shows the concept involved.


		|
		|
		|			            *
		|			 .     *   .         ^DN
	    DN  |			  *    |            -----*SCALE=SLOPE
		|	             *         |            ^EXPO 
		|	.       *   .          | ^DN
		|          *___________________|
 		|     *        ^EXPO
	      DC|*
		|
		|____________________________________
                0          EXPOSURE

Explanation of FIGURE 1:
		^ - is used to represent a delta
  		* - is used to represent a straight solid line
		. - are points of exposure


  EXAMPLES:

	dc INP=(A,B,C,D,E) OUT=(DC,SLOPE) EXPO=(3.0,4.0,1.0,2.5,2.2) 	SCALE=2.0

     DC will fit a line to these points in a light transfer sequence and
     output a zero exposure level picture and a slope picture which is
     multiplied by 2.

     RESTRICTIONS:

	1. All the input frames must have as many or more lines and samples
	   as the first input.

WRITTEN BY: Joel Mosher				1 May 1977

COGNIZANT PROGRAMMER: Helen De Rueda		  Feb 1984

Made portable for UNIX by: Alan Scop (CRI)      5 SEP 1994