Introduction to data modeling

EASI provides a powerful and convenient way to manipulate image data in database files through the use of its Modeling facility. The MODEL command is used to introduce a block of commands which are to be applied over an area of a database. The basic syntax of the MODEL commands is 

MODEL [ON filespec [OVER window_spec]]
  Modeling_command_list
ENDMODEL

The filespec may be a database name, or the handle returned by a previous DBOpen() call. The window_spec specifies a subwindow of the database to operate on, and is given in XOff, YOff, XSize, YSize format.

The Modeling_command_list can be any of a variety of commands. The most important command that can be applied in a model is a Modeling assignment. This is a normal assignment (LET) statement, using database channel specifiers for "assigned to", and "source" values.

  1. Special variables
  2. Using image channels
  3. Subscript expressions
  4. Using bitmap segments
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