BLO

Description

BLO performs specified logical operations on one or two bitmap segments stored in a database file.

Parameters

blo(file, logfunc, dbsn, dbsd, dbib, dbob, lasc)

Name	Type	Caption	Length	Value range
FILE *	str	Input file name	1 -
LOGFUNC *	str	Function: AND/OR/XOR/SUB/NOT	2 - 3	AND, OR, XOR, SUB, NOT
DBSN	str	Output segment name	0 - 8
DBSD	str	Output segment description	0 - 64
DBIB *	List[int]	Input bitmap channels	1 - 2	-1024 -
DBOB	List[int]	Output bitmap	0 - 1
LASC	List[int]	Last segment created	0 - 1

* Required parameter

Parameter descriptions

FILE

Specifies the name of the PCIDSK file in which the input and output bitmap segments reside.

LOGFUNC

The simple logical operators have the following truth tables:

   i|j| i AND j       i|j| i OR j        i|j| i XOR j
  +-+-+--------       -+-+-------        -+-+--------
   0|0|    0          0|0|   0           0|0|    0
   0|1|    0          0|1|   1           0|1|    1
   1|0|    0          1|0|   1           1|0|    1
   1|1|    1          1|1|   1           1|1|    0

   i|j| i SUB j = i AND NOT j            i| NOT i
  +-+-+--------                          -+------
   0|0|    0                             0|   1
   0|1|    0                             1|   0
   1|0|    1
   1|1|    0

DBSN

Bitmap segment names are no longer supported, so the DBSN value is ignored. The DBSN parameter still remains to provide compatability for legacy applications.

DBSD

Describes (in up to 64 characters) the contents or origins of the output bitmap.

DBIB

Specifies two input bitmap channels for logical operation. Two bitmaps are required for all operations, except "NOT", which requires only one.

 DBIB=i,[j]

DBOB

Optionally specifies the output bitmap segment to receive the generated logical result.

If this parameter is explicitly specified, the bitmap segment is overwritten. If it is not specified, a new bitmap segment is created.

LASC

The segment number of the newly created bitmap segment is saved in this output parameter.

Details

BLO performs logical operations on two database bitmap segments, unless the logical "NOT" has been specified, in which case only one bitmap is allowed.

If the output bitmap is specified, BLO writes the results of the logical operation to the specified segment number provided it exists and is of bitmap type (101). This bitmap segment will be overwritten without warning.

To obtain a list of existing bitmap segments, ASL can be used with the ASLT parameter set to 101. In this case, the bitmap layer name and bitmap layer description are ignored. (Use MAS to change these.)

If no output bitmap is specified, BLO creates a new bitmap segment. A segment name of up to 8 characters must be specified and an optional 64-character description may be specified.

When a new bitmap segment is created, a message appears on the terminal providing the segment number of the newly created segment. This new segment number is saved in the LASC parameter.

Example

Using BLO, generate a new bitmap segment that uses the logical operator "OR" between the two input segments.

from pci.blo import blo

file        =   "irvine.pix"    # input file name
logfunc     =   "OR"            # logical operation
dbsn        =   "OR1.4"         # segment name
dbsd        =   "Logical OR"    # segment descriptor
dbib        =   [9,10]          # input bitmaps
dbob        =   []              # output bitmap
lasc        =   []

blo( file, logfunc, dbsn, dbsd, dbib, dbob, lasc )