PCE

Description

Encodes an input channel into three output channels (red, green, and blue components) using a pseudocolor table held in a database segment.

Parameters

Name	Type	Length	Value range
Encoding Mode	String	0 - 1	NORM | OVER Default: NORM
Input: Input raster channel *	Raster port	1 - 1
InputPCT: Input pseudocolor table channel *	PCT port	1 - 1
OutputPCE: Output raster channels *	Raster port	3 - 3

* Required parameter

Parameter descriptions

Encoding Mode

Specifies the pseudocolor encoding mode.

Input: Input raster channel

Specifies the input channel to encode.

The input channel should be 8-bit.

InputPCT: Input pseudocolor table channel

Specifies the input segment (type 171) that holds the pseudocolor table.

OutputPCE: Output raster channels

Specifies the three output channels to receive the encoding results (red, green, and blue).

Details

PCE is used to encode an input channel (DBIC) into three output channels (DBOC, where DBOC(1) = red output channel, DBOC(2) = green, and DBOC(3) = blue) using a pseudocolor table held in a database segment (DBPCT).

A special feature of PCE is that pixel values of zero in the input channel (DBIC) are NOT encoded into the three output channels if the encoding method (ENCODING) is set to "OVER". This leaves the underlying values unaltered, allowing the input channel to be overlaid on the original data already in the output channels. For example, given that the specified output channels (DBOC) contain image data and the input channel (DBIC) is a classification from the MLC function, only the 'classified' pixels would be encoded, because unclassified (or null-class) pixels have a value of zero. The result would be a false color image with classified regions embedded in the image.

The primary use of PCE is to create red, green, and blue color channels for output to a video display or hardcopy output. Often, these channels can be written to tape and sent to other installations for photographic or color plotter reproduction.

For example, given the following pseudocolor table and 4x4 initial data channels:

 Pseudocolor table
 input   output        DBIC       DBOC(1)     DBOC(2)     DBOC(3)
 level   R  G  B                  (Red)       (Green)     (Blue)

   0     7  7  7      0 0 0 0     1 1 1 5     4 4 4 3     3 3 2 3
   1     8  3  0      1 1 0 0     1 1 1 1     1 1 1 1     9 9 9 9
   2     8  5  1      2 3 0 0     1 1 1 1     1 1 1 1     9 9 9 9
   3     2  0  1      0 0 0 0     1 1 1 1     1 1 1 1     9 9 9 9
   4     9  9  9
  ...
  255    .  .  .

With the encoding mode set to "NORM", output for the three output channels would be as follows:

            DBOC(1)        DBOC(2)        DBOC(3)

            7 7 7 7        7 7 7 7        7 7 7 7
            8 8 7 7        3 3 7 7        0 0 7 7
            8 2 7 7        5 0 7 7        1 1 7 7
            7 7 7 7        7 7 7 7        7 7 7 7

With the encoding method set to "OVER", output for the three output channels would be as follows:

            DBOC(1)        DBOC(2)        DBOC(3)

            1 1 1 5        4 4 4 3        3 3 2 3
            8 8 1 1        3 3 1 1        0 0 9 9
            8 2 1 1        5 0 1 1        1 1 9 9
            1 1 1 1        1 1 1 1        9 9 9 9

Acknowledgements

PCE functionality is based on a program submitted by Mit Tilkov of Cominco Ltd., developed using B.C. Research facilities.