This sample demonstrates how to apply user defined raster function and mosaic rules to an ImageryLayer layer.
The imagery layer's raster function uses a raster function chain to reclassify and re-render the original land cover categories into two new categories: forest and non-forest.
// Defines a Remap raster function. Remap reclassifies pixel
// values to new values. In this case we want to separate
// two land cover types: forested areas and non-forested areas
const remapRF = new RasterFunction({
functionName: "Remap",
functionArguments: {
// pixel values of forest categories are 41, 42, and 43
// according to the raster attribute table.
// The InputRanges property defines the ranges of initial pixel values to remap
// Three ranges: [0, 41], [41, 44], and [44, 255] are defined to extract forest pixels.
inputRanges: [0, 41, 41, 44, 44, 255],
// non-forest pixels (0-41 and 44-255) are remapped to a value of 1,
// forest pixels (41-44) are remapped to a value of 2.
outputValues: [1, 2, 1],
// $$(default) refers to the entire image service,
// $2 refers to the second image of the image service
raster: "$$"
}
});
// The Colormap raster function adds color to each pixel
// based on its pixel value
const colorRF = new RasterFunction({
functionName: "Colormap",
functionArguments: {
colormap: [
// non-forest pixels (value of 1) are assigned
// a yellowish color RGB = [253, 254, 152]
[1, 253, 254, 152],
// forest pixels (value of 2) are assigned
// a greenish color RGB = [2, 102, 6]
[2, 2, 102, 6]
],
// Setting the previous raster function to the Raster
// property of a new raster function allows you to chain functions
raster: remapRF
},
outputPixelType: "U8"
});
const layer = new ImageryLayer({
url: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/NLCDLandCover2001/ImageServer",
// apply the most recent raster function to the chain
rasterFunction: colorRF,
mosaicRule: mosaicRule
});
Mosaic rule changes the mosaic schema of all raster items in the referenced image service. Once set, it generates a map in which green areas represent forested while yellow areas are non-forest.