RasterFunction

Raster functions specify processing to be done to the image service. They allow the mosaic image service to deliver a dynamically mosaicked image and they can be used to enhance the mosaicked image product by applying processing operations such as image enhancements, and image algebra. See raster functions for a list of functions and their arguments. The following image shows a landcover ImageryLayer rendered with two chained client-side raster functions used to reclass pixel values (Remap) and assign each pixel a new color (Colormap).

Chaining raster functions is accomplished by setting the Raster argument in the functionArguments property to another defined raster function. See example below on chaining a Remap raster function with a Colormap.

let remapRF = new RasterFunction();
remapRF.functionName = "Remap";
remapRF.functionArguments = {
  InputRanges: [-3,10,11,37], // remap pixels with values -3 to 10 to now have value of 1
  OutputValues: [1,2],        // remap pixel values from 11 to 37 to have a value of 2
  Raster: "$$"  // Apply remap to the image service
};
remapRF.outputPixelType = "u8";

let colorRF = new RasterFunction();
colorRF.functionName = "Colormap";
colorRF.functionArguments = {
  Colormap: [
    [1, 255, 0, 0],  // Symbolize pixels with value of 1 using red color
    [2, 0, 255, 0]   // Symbolize pixels with value of 2 using green color
  ],
  Raster : remapRF  // Apply Colormap to output raster from the remap rasterFunction
};

imageLayer.rasterFunction = colorRF;

The following code snippet shows how convenience methods from the rasterFunctionUtils module can be used when applying a raster function to an imagery or imagery tile layer.

// apply NDVI and colormap raster function to an imagery tile layer
// use rasterFunctionUtils convenience methods to create raster functions
const ndvi = rasterFunctionUtils.bandArithmeticNDVI({
  nirBandId: 4,
  redBandId: 3,
  scientificOutput: false
});

 const colormap = rasterFunctionUtils.colormap({
  colorRampName: "NDVI3",
  raster: ndvi
});
layer.rasterFunction = colormap;