ImageryLayer - client side pixel filter

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This sample uses an instance of ImageryLayer to visualize global sea temperature by filtering pixel values on the client-side. You can filter out the temperature values on the imagery layer by adjusting the slider thumbs. Filtering is accomplished through the pixelFilter property of the ImageryLayer. The function defined for this property determines how users can dynamically change the raster image on the client-side.

The service data is managed using a multidimensional mosaic dataset. Esri reserves the right to change or remove this service at any time and without notice.

The pixelFilter property is used in this sample to add a custom continuous color ramp to the pixels. The color is determined based on the temperature or the value of the pixel. To assign a color to the pixels, you must loop through all the pixels displayed in the view.

<html>
  <head>
    <meta charset="utf-8" />
    <meta
      name="viewport"
      content="initial-scale=1,maximum-scale=1,user-scalable=no"/>
      <title>ImageryLayer - client side pixel filter | Sample | ArcGIS API for JavaScript 4.20</title>

    <link rel="stylesheet" href="https://js.arcgis.com/4.20/esri/themes/light/main.css" />
    <script src="https://js.arcgis.com/4.20/"></script>

    <style>
      html,
      body,
      #viewDiv {
        padding: 0;
        margin: 0;
        height: 100%;
        width: 100%;
      }

      .slider {
        width: 100%;
        height: 60px;
      }

      #infoDiv {
        padding: 10px;
        width: 500px;
      }
    </style>

    <script>
      require([
        "esri/Map",
        "esri/views/MapView",
        "esri/layers/ImageryLayer",
        "esri/layers/support/DimensionalDefinition",
        "esri/layers/support/MosaicRule",
        "esri/widgets/Slider",
        "esri/core/watchUtils"
      ], function (
        Map,
        MapView,
        ImageryLayer,
        DimensionalDefinition,
        MosaicRule,
        Slider,
        watchUtils
      ) {
        // The URL to an image layer representing sea temperature
        const url =
          "https://sampleserver6.arcgisonline.com/arcgis/rest/services/ScientificData/SeaTemperature/ImageServer";

        const map = new Map({
          basemap: "dark-gray-vector"
        });

        const view = new MapView({
          container: "viewDiv",
          map: map,
          zoom: 2,
          center: [-32, 28],
          popup: {
            actions: []
          }
        });

        /**********************************************************************************************
         * Variable water_temp describes the water temperature, it has both depth and time dimensions.
         * This snippet sets water_temp to a specific depth and a specific time by defining the
         * multidimensionalDefinition property of a MosaicRule object.
         **********************************************************************************************/
        const dimInfo = []; // Define dimensional definition as array

        // Multidimensional information of image service can be viewed at this
        // Service/multiDimensionalInfo
        // DEPTH: show only temperatures at sea surface
        dimInfo.push(
          new DimensionalDefinition({
            dimensionName: "StdZ", // Water depth
            values: [0], // Sea surface or 0ft
            isSlice: true
          })
        );

        // TIME: only show temperatures for the week of April 7, 2014
        dimInfo.push(
          new DimensionalDefinition({
            dimensionName: "StdTime", // time temp was recorded
            values: [1396828800000], // Week of April 7, 2014
            isSlice: true
          })
        );

        const mr = new MosaicRule({
          multidimensionalDefinition: dimInfo
        });

        const layer = new ImageryLayer({
          url: url,
          pixelFilter: maskPixels,
          mosaicRule: mr,
          // The popup will display the temperature at the clicked location
          popupTemplate: {
            title: "Sea Surface Temperature",
            content: "{Raster.ServicePixelValue}° Celsius"
          }
        });

        // Add sea temperature layer to the map
        map.add(layer);

        // Slider to mask imagery layer based on its pixel values
        const pixelSlider = new Slider({
          container: "pixelSlider",
          min: -3,
          max: 37,
          steps: 1,
          values: [-3, 37],
          visibleElements: {
            labels: true,
            rangeLabels: true
          }
        });
        view.ui.add("infoDiv", "bottom-left");
        pixelSlider.on(["thumb-drag", "thumb-change"], updatePixelFilter);

        let currentMin, currentMax;

        // This function is called when user is moves the slider thumb to
        // the pixel values of imagery layer based on temperature
        // if pixel value lies between slider min and max
        function updatePixelFilter() {
          distance = pixelSlider.values[0];
          currentMin = Math.floor(pixelSlider.values[0]);
          currentMax = Math.floor(pixelSlider.values[1]);
          document.getElementById("pixelVal").innerHTML =
            `Currently displaying locations with sea temperatures from ${currentMin} °C to ${currentMax} °C`;
          layer.redraw();
        }

        // /**********************************************************
        // * The PixelFilter function. This function is used to color the
        // * pixels. By default, each pixel has one band containing
        // * a temperature value. We will replace the single band with
        // * three bands - red, green, and blue to give color to the layer.
        // *********************************************************/

        function maskPixels(pixelData) {
          if (pixelData == null || pixelData.pixelBlock == null) {
            return;
          }
          if (currentMin == null || currentMax == null) {
            // layer is loaded get the min and max temp values from the layer
            updatePixelFilter();
          }

          // The pixelBlock stores the values of all pixels visible in the view
          const pixelBlock = pixelData.pixelBlock;
          // The pixels visible in the view
          const pixels = pixelBlock.pixels;
          let mask = pixelBlock.mask;

          // The number of pixels in the pixelBlock
          const numPixels = pixelBlock.width * pixelBlock.height;

          // Get the min and max values of the data in the current view
          const minVal = pixelData.pixelBlock.statistics[0].minValue;
          const maxVal = pixelData.pixelBlock.statistics[0].maxValue;

          // Calculate the factor by which to determine the red and blue
          // values in the colorized version of the layer
          const factor = 255.0 / (maxVal - minVal);
          if (pixels == null) {
            return;
          }

          // Get the pixels containing temperature values in the only band of the data
          const tempBand = pixels[0];
          const p1 = pixels[0];
          // Create empty arrays for each of the RGB bands to set on the pixelBlock
          const rBand = new Uint8Array(p1.length);
          const gBand = new Uint8Array(p1.length);
          const bBand = new Uint8Array(p1.length);

          if (mask == null) {
            mask = new Uint8Array(p1.length); //mask = new Uint8Array(p1.length);
            mask.fill(1);
            pixelBlock.mask = mask;
          }

          // Loop through all the pixels in the view
          for (let i = 0; i < numPixels; i++) {
            // skip noData pixels
            if (mask[i] ===0) {
              continue;
            }
            const tempValue = tempBand[i];
            const red = (tempValue - minVal) * factor;
            mask[i] =
              p1[i] >= Math.floor(currentMin) && p1[i] <= Math.floor(currentMax)
                ? 1
                : 0;

            //apply color based on temperature value of each pixel
            if (mask[i]) {
              // p[i] = Math.floor((p1[i] - minVal) * factor);
              rBand[i] = red;
              gBand[i] = 0;
              bBand[i] = 255 - red;
            }
          }

          // Set the new pixel values on the pixelBlock
          pixelData.pixelBlock.pixels = [rBand, gBand, bBand]; //assign rgb values to each pixel
          pixelData.pixelBlock.statistics = null;
          pixelData.pixelBlock.pixelType = "u8";
        }


        // Display popup when the layer view loads
        view.whenLayerView(layer).then(function (layerView) {
          watchUtils.whenFalseOnce(layerView, "updating", function (newVal) {
            view.popup.open({
              title: "Sea Surface Temperature",
              content:
                "Click anywhere in the oceans to view the sea temperature at that location.",
              location: view.center
            });
          });
        });
      });
    </script>
  </head>

  <body>
    <div id="viewDiv"></div>
    <div id="infoDiv" class="esri-widget">
      <h4 class="esri-editor__title esri-heading">
        Sea Surface Temperature (°C) on April 7, 2014
      </h4>
      <br />
      <div id="pixelVal"></div>
      <div id="pixelSlider" class="slider"></div>
    </div>
  </body>
</html>

Since the image service has multidimensional information, you can set the multidimensionalDefinition property in the MosaicRule object to apply a pixelFilter based on water temperature at a specific water depth and time.

MapView

ImageryLayer

RasterFunction

ArcGIS API for JavaScriptSample Code

ImageryLayer - client side pixel filter

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