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This article provides a script that applies a multi-color ramp to single-band image.
'-- The following script applies a "red to blue to white"
'-- color ramp to a single band image legend.
'-- It assumes that the active doc is a view and that
'-- one and only one theme is active in that view and that the
' active theme is an image theme with a single band image legend.
theView = av.GetActiveDoc
theTheme = theView.GetActiveThemes.Get(0)
theLegend = theTheme.GetLegend
'-- Get the color map from the image legend. This is easiest.
'-- You can create a new color map using ColorMap.MakeRandom,
'-- ColorMap.MakeNominal, or any of the ColorMap.Make* request.
'-- It doesn't really matter which one you use as long as
'-- you set the size to 256. If you make a new color map
'-- then before theTheme.UpdateLegend you need to do
theColorMap = theLegend.GetColorMap
'-- Create a red to blue color map and a blue to white
'-- color map each with 128 colors
redBlueColorMap = ColorMap.MakeRamp(128,Color.GetRed,Color.GetBlue)
blueWhiteColorMap = ColorMap.MakeRamp(128,Color.GetBlue,Color.GetWhite)
'-- Use the two new 128 color maps to apply colors
'-- to the original 256 color map or a new 256 color map.
for each i in 0..127
for each i in 128..255
'-- Update the legend and redraw theme.
'-- You can set a lookup if needed. For example, your image
'-- data went from 0 to 100 and you wanted to stretch
'-- that data across the entire color map. The following
'-- two lines of code will do this. Place these two lines
' before theTheme.UpdateLegend above.
'newLookup = LinearLookup.MakeLine(Point.Make(0,0),Point.Make(100,255))
'-- It is best to start from the current image legend of an image theme,
'-- but you can start from scratch. The code below does this.
'-- Instead of theTheme.UpdateLegend above you would
'-- use theTheme.SetLegend(newLegend). It is best to set a
'-- color map of 256 colors.
'anImageLookup = LinearLookup.MakeLine(Point.Make(0,0),Point.Make(255,255))
'aColorMap = ColorMap.MakeRamp(256,Color.GetYellow,Color.GetBlue)
'newLegend = SingleBandLegend.Make(0,anImageLookup,aColorMap)
'-- The above lookup is the same as the identify lookup,
'-- or IdentityLookup.Make. It maps the values in the image
'-- to the same value in the color map.