DCL ARRAY(1) FLOAT DEC(6);            /* Array for conversion factors  */
     /*       proj-id alg  count  alg-data                                 */
     CALL IMRCVB(3,    10,   0,    ARRAY); /* Define conversion to bi-level */

• The first parameter, 3, is, as usual, the projection identifier.

• The second parameter, 10, specifies halftoning type A. This is best for intricate pictures.
  Other possible values are:

  0

  Device-dependent (the default). For the 3117 and 3118 this is the same as 1.

  1

  Threshold. A threshold is defined for comparison with each source pixel. Pixels above the threshold gray-level specified in ARRAY(1) become white and below it become black.

  11

  Halftoning type B, best when gray-levels vary gradually.

• The next parameter is a count, specifying the number of elements in the array parameter that follows. You are recommended to use a value of 0 if you are specifying the default algorithm in the second parameter.

• The last parameter is the array of factors, if any, for the specified algorithm.
  For algorithm 1, ARRAY(1) specifies the required threshold level as a number in the range 0 through 1, where 0 is black and 1 is white. The default threshold is 0.5.
  The 3117 and 3118 scanners provide three threshold levels only, depending on ARRAY(1) values as follows:

  0 through 0.25

  Dark original

  >0.25 through <0.75

  Normal original

  0.75 through 1.0

  Light original.

  For algorithm 10 or 11, the fourth parameter is not used.