Example of loading a segmentation 
          mask on the image.
          You can modify the mask using Brush tool.
          (press ctrl to delete instead of adding)
          
          Switch label 
          UndoRedo
          
          

            let demoFiles = [];
            let counter = 0;

            const getDemoFileNames = function () {
              let demoFileList = [];
              for (let i = 1; i < 25; i++) {
                let filename = "anon" + i;
                demoFileList.push(filename);
              }
              return demoFileList;
            };

            // init all
            larvitar.initializeImageLoader();
            larvitar.initializeCSTools();
            larvitar.store.initialize();
            larvitar.store.addViewport("viewer");
            larvitar.registerNRRDImageLoader();

            async function createFile(fileName, cb) {
              let response = await fetch("./demo/" + fileName);
              let data = await response.blob();
              let file = new File([data], fileName);
              demoFiles.push(file);
              counter++;
              if (counter == 24) {
                cb();
              }
            }

            function renderSerie() {
              larvitar.resetLarvitarManager();
              larvitar.readFiles(demoFiles, function (seriesStack, err) {
                if (seriesStack) {
                  // render the first series of the study
                  let seriesId = _.keys(seriesStack)[0];
                  let serie = seriesStack[seriesId];
                  larvitar.renderImage(serie, "viewer").then(function () {
                    larvitar.addDefaultTools();
                    demoFiles = [];
                    loadMasks();
                  });
                } else {
                  console.log(err);
                }
              });
            }

            let demoFileList = getDemoFileNames();

            _.each(demoFileList, function (demoFile) {
              createFile(demoFile, renderSerie);
            });

            /**
            * Load an image as in base example, then:
            **/

            async function loadMasks() {
              larvitar.initSegmentationModule();
      
              // fetch data
              let response = await fetch("./demo/" + "segmentation.nrrd");
              let data = await response.blob();
              let nrrd_file = new File([data], "segmentation.nrrd");
              // read file
              let reader = new FileReader();
              reader.readAsArrayBuffer(nrrd_file);
              reader.onload = function () {
                // create volume
                let volume = larvitar.importNRRDImage(reader.result);
                // define mask properties
                let properties = {
                  // color: "#00ff00",
                  opacity: 0.2,
                  labelId: 0
                };
                // add to viewport
                larvitar
                  .addSegmentationMask(properties, volume.data, "viewer")
                  .then(() => {
                    // activate brush on this labelmap
                    larvitar.setActiveLabelmap(0, "viewer");
                    larvitar.setToolActive("Brush");
                  });
              };
            }
      
            let activeLabel = 1;
            function switchLabel() {
              let nextLabel = activeLabel == 1 ? 2 : 1;
              larvitar.setActiveSegment(nextLabel, "viewer");
              activeLabel = nextLabel;
              let btn = document.getElementById("btn-label");
              let btnClass = btn.className;
              if (activeLabel == 1) {
                btn.className = btnClass.replace("warning", "danger");
              } else {
                btn.className = btnClass.replace("danger", "warning");
              }
            }
            function undo() {
              larvitar.undoLastStroke("viewer");
            }
            function redo() {
              larvitar.redoLastStroke("viewer");
            }

            /**
            * Undo: larvitar.undoLastStroke("viewer");
            * Redo: larvitar.redoLastStroke("viewer");
            * Switch: larvitar.setActiveSegment(1|2, "viewer");
            */