3 Color Maximum

This operator converts input values to a color and creates a variable where the color for a sample is the maximum scaled color value of the 3 input operands. The settings for this operator are entered on the 3 Color Maximum page of the Variable Properties dialog box.

It accepts operands with the following data types:

Operand 1:

  • Linear
  • Power dB
  • Sv
  • TS
  • Unspecified dB

Operand 2:

  • Linear
  • Power dB
  • Sv
  • TS
  • Unspecified dB

Operand 3:

  • Linear
  • Power dB
  • Sv
  • TS
  • Unspecified dB

Settings

The 3 Color Maximum Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:

Operands page

3 Color Maximum page

Setting

Description

Color display minimum

Enter a value for the Color display minimum for the operand.

Minimum Color

Displays the Minimum color for the operand. Click the color to select a new Minimum color.

Color display range

Enter a value for the Color display range for the operand.

Maximum Color

Displays the Maximum color for the operand. Click the color to select a new Maximum color.

Notes:

  • The default colors on the 3 Color Maximum page do not represent pure RGB colors.
  • Display settings for a 3 color maximum virtual variable can be changed using keyboard shortcuts.
  • It may also be useful to specify the Color scheme on the Echogram Display page of 3 Color Maximum Variable Properties dialog box.

Algorithm

The 3 color maximum operator takes 3 input operands, transforms them according to assigned color settings and creates a virtual variable containing samples whose colors represent the maximum of the transformed operands. The algorithm is based on that described by Kloser et al.

Scaled value

Each operand's sample values are transformed to scaled values. Samples with No_data value, result in an output sample color that represents the No_data color for the color scheme specified on the Echogram Display page of the Variable Properties dialog box. The calculation is applied within the domain of the data type. That is, dB calculations in the dB domain and linear calculations in the linear domain etc.

The Scaled value algorithm is:

Scaled value = (Sample value – Color display minimum) / Color display range

Where:

Sample value

is the value of the sample in the original operand

Color display minimum

is Color display minimum on the 3 Color Maximum page of the Variable Properties dialog box.

Color display range

is the Color display range on the 3 Color Maximum page of the Variable Properties dialog box.

Output color

The scaled values from the operands are compared. The greatest scaled value (of the operands) becomes the Output color for the sample in the virtual variable.

If the greatest of the scaled values is

greater than 1

the output color is set to the "above threshold" color for the Color scheme on the Echogram Display page of the Variable Properties dialog box.

between 0 and 1 the output color is specified by the settings of the operand which had the greatest scaled value. If there is a tie the earlier operand wins (that is operand 1 before operand 2 before operand 3). The Output color is the linear interpolation between the Minimum color and the  Maximum color specified on the 3 Color Maximum page of the Variable Properties dialog box.
less than 0

the output color is the “below threshold” color for the Color scheme on the Echogram Display page of the Variable Properties dialog box.

See also

About virtual variables
Operator licensing in Echoview