Add download image button

Signed-off-by: Justin Georgi <justin.georgi@gmail.com>

modules/glmv.js

@@ -392,4 +392,29 @@ enableViewer = function() {
     previewMv[0].disableTap = false
     previewMv[0].toggleAttribute('camera-controls', true)
     return previewMv[0]
+}
+
+/**
+ * Use the model viewer methods to get image 
+ * of current view and download
+ * 
+ * @param {string} defName wiki page name to use as base file name
+ */
+downloadImage = function(defName) {
+    const imgName = defName.substring(5).split('.')[0]
+    const mView = $('model-viewer')[0]
+
+    const dlA = document.createElement('a')
+    dlA.setAttribute('download',imgName + '.png')
+
+    const reader = new FileReader()
+    reader.addEventListener("load", () => {
+        dlA.setAttribute('href',reader.result)
+        dlA.click()
+    },{once: true})
+
+    mView.toBlob(null, null, true)
+        .then(imgBlob => {
+            reader.readAsDataURL(imgBlob)
+        })
 }