DICOM Overlays

Adds 'overlayPlaneModule' type returning an array of DICOM overlays.
This array is then added the 'overlays' propertry of the image.

This is then read by the overlays tool see - [cornerstonejs/cornerstoneTools#788](cornerstonejs/cornerstoneTools#809)

see issue [cornerstonejs/cornerstoneTools#780](cornerstonejs/cornerstoneTools#780)
see DICOM overlays standard - http://dicom.nema.org/dicom/2013/output/chtml/part03/sect_C.9.html

src/imageLoader/wadors/metaData/metaDataProvider.js

@@ -130,6 +130,47 @@ function metaDataProvider (type, imageId) {
     };
   }
 
+  if (type === 'overlayPlaneModule') {
+    const overlays = [];
+
+    for (let overlayGroup = 0x00; overlayGroup <= 0x1E; overlayGroup += 0x02) {
+      let groupStr = `x60${overlayGroup.toString(16)}`;
+      if (groupStr.length === 4) {
+        groupStr = `x600${overlayGroup.toString(16)}`;
+      }
+
+      const data = getValue(metaData[`${groupStr}3000`]);
+      if (!data) {
+        continue;
+      }
+
+      const pixelData = [];
+      for (let i = 0; i < data.length; i++) {
+        for (let k = 0; k < 8; k++) {
+          const byte_as_int = metaData.Value[data.dataOffset + i];
+          pixelData[i * 8 + k] = (byte_as_int >> k) & 0b1; // eslint-disable-line no-bitwise
+        }
+      }
+
+      overlays.push({
+        rows: getNumberValue(metaData[`${groupStr}0010`]),
+        columns: getNumberValue(metaData[`${groupStr}0011`]),
+        type: getValue(metaData[`${groupStr}0040`]),
+        x: getNumberValue(metaData[`${groupStr}0050`], 1) - 1,
+        y: getNumberValue(metaData[`${groupStr}0050`], 0) - 1,
+        pixelData,
+        description: getValue(metaData[`${groupStr}0022`]),
+        label: getValue(metaData[`${groupStr}1500`]),
+        roiArea: getValue(metaData[`${groupStr}1301`]),
+        roiMean: getValue(metaData[`${groupStr}1302`]),
+        roiStandardDeviation: getValue(metaData[`${groupStr}1303`])
+      });
+    }
+
+    return {
+      overlays
+    };
+  }
 }
 
 export default metaDataProvider;