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Settings |
Linear response |
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Sample non-linear response |
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Number of color steps = 2 Color 1 = black Color 2 = white Color display minimum = -100 dB re m-1 Color display range = 100 dB re m-1 |
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Color response curves are described in two sections:
Overview of color response curves
Defining color response curves
Ordinarily color schemes are interpreted linearly. The definition and application of any color scheme includes the following key parameters:
Number of color steps
One color definition for each step
Color display minimum
Color display range
The Number of color steps and each color are defined in the color scheme itself. Many are built-in but you can also define your own using Echocolor.
The Color display minimum and Color display range are specified when the color scheme is selected (i.e. on the Display page of the Variable Properties dialog box or the General page of the Scene properties dialog box). These two parameters define the mapping of data to color. The data value may be of any valid data type but for the purposes of illustration consider an Sv display with this very simple color scheme:
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Settings |
Linear response |
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Sample non-linear response |
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Number of color steps = 2 Color 1 = black Color 2 = white Color display minimum = -100 dB re m-1 Color display range = 100 dB re m-1 |
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With the default (linear) color response curve the transition from black to white lies at -50 dB re mm-1, with the simple non-linear color response illustrated the transition lies instead at -10 dB rem-1.
Color response curves are defined on the Response curves page of the EV File properties dialog box. The response curves underlying the two color legends above might look like this:
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Linear response |
Sample non-linear response |
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The standard linear response curve has two nodes, one at bottom left and one at top right. Non-linear response curves can be defined by adding nodes to this curve. Any number of nodes can be added to define a curve of any shape and complexity desired which is used to modify the standard linear palette for display purposes. For example:
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Sample complex color response curve |
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R |
In it's general form the color response curve can be expressed as a mathematical function:
In = f(Out)
where:
In = the standard color index for a particular data value
Out = the resulting color index for a particular data value
f(x) = the color response curve
Echoview uses this function to create a new palette with 2048 color steps which is then used for display purposes (standard palettes may have as many as 1024 colors).
Echoview requires that for any one value of Out there is one and only one corresponding value of In (i.e. that f is a mathematical function). The placement and movement of nodes on the color response curve is restricted to enforce this requirement.
About color schemes
About Echocolor
Response curves page of the EV File properties dialog box
