Parent Topic: STR

ALGORITHM

The contrast stretch function has the following form:

  F(X) = A * (X - ISTR(1)) ** EXPO + OSTR(1) 
                                        ISTR(1) < X < ISTR(2)

 X              Input grey-level value
 F(X)           Output grey-level value
 A              Scaling factor
 EXPO           Power exponent (must be positive value)
 ISTR(1)        Minimum input grey-level value (must be <= ISTR(2))
 ISTR(2)        Maximum input grey-level value (must be >= ISTR(1))
 OSTR(1)        Minimum output grey-level value
 OSTR(2)        Maximum output grey-level value

 If OSTR(1) > OSTR(2), the result is a `negative' image.

The formula for determining the scaling factor A is as follows:

                OSTR(2) - OSTR(1)
        A = ---------------------------
            (ISTR(2) - ISTR(1)) ** EXPO

Parent Topic: STR
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