Merge with qr-improvements.

Change QR code ops to use ArrayBuffer.
Add new function to Utils to convert a string to arraybuffer.

src/core/lib/Magic.mjs

@@ -312,6 +312,11 @@ class Magic {
                 return;
             }
 
+            // If the recipe returned an empty buffer, do not continue
+            if (_buffersEqual(output, new ArrayBuffer())) {
+                return;
+            }
+
             const magic = new Magic(output, this.opPatterns),
                 speculativeResults = await magic.speculativeExecution(
                     depth-1, extLang, intensive, [...recipeConfig, opConfig], op.useful, crib);
@@ -395,7 +400,12 @@ class Magic {
         const recipe = new Recipe(recipeConfig);
         try {
             await recipe.execute(dish);
-            return dish.get(Dish.ARRAY_BUFFER);
+            // Return an empty buffer if the recipe did not run to completion
+            if (recipe.lastRunOp === recipe.opList[recipe.opList.length - 1]) {
+                return dish.get(Dish.ARRAY_BUFFER);
+            } else {
+                return new ArrayBuffer();
+            }
         } catch (err) {
             // If there are errors, return an empty buffer
             return new ArrayBuffer();

src/core/lib/QRCode.mjs

@@ -0,0 +1,91 @@
+/**
+ * QR code resources
+ *
+ * @author j433866 [j433866@gmail.com]
+ * @copyright Crown Copyright 2019
+ * @license Apache-2.0
+ */
+
+import OperationError from "../errors/OperationError";
+import jsQR from "jsqr";
+import qr from "qr-image";
+import jimp from "jimp";
+import Utils from "../Utils";
+
+/**
+ * Parses a QR code image from an image
+ *
+ * @param {ArrayBuffer} input
+ * @param {boolean} normalise
+ * @returns {string}
+ */
+export async function parseQrCode(input, normalise) {
+    let image;
+    try {
+        image = await jimp.read(input);
+    } catch (err) {
+        throw new OperationError(`Error opening image. (${err})`);
+    }
+
+    try {
+        if (normalise) {
+            image.rgba(false);
+            image.background(0xFFFFFFFF);
+            image.normalize();
+            image.greyscale();
+        }
+    } catch (err) {
+        throw new OperationError(`Error normalising iamge. (${err})`);
+    }
+
+    const qrData = jsQR(image.bitmap.data, image.getWidth(), image.getHeight());
+    if (qrData) {
+        return qrData.data;
+    } else {
+        throw new OperationError("Could not read a QR code from the image.");
+    }
+}
+
+/**
+ * Generates a QR code from the input string
+ *
+ * @param {string} input
+ * @param {string} format
+ * @param {number} moduleSize
+ * @param {number} margin
+ * @param {string} errorCorrection
+ * @returns {ArrayBuffer}
+ */
+export function generateQrCode(input, format, moduleSize, margin, errorCorrection) {
+    const formats = ["SVG", "EPS", "PDF", "PNG"];
+    if (!formats.includes(format.toUpperCase())) {
+        throw new OperationError("Unsupported QR code format.");
+    }
+
+    let qrImage;
+    try {
+        qrImage = qr.imageSync(input, {
+            type: format,
+            size: moduleSize,
+            margin: margin,
+            "ec_level": errorCorrection.charAt(0).toUpperCase()
+        });
+    } catch (err) {
+        throw new OperationError(`Error generating QR code. (${err})`);
+    }
+
+    if (!qrImage) {
+        throw new OperationError("Error generating QR code.");
+    }
+
+    switch (format) {
+        case "SVG":
+        case "EPS":
+        case "PDF":
+            return Utils.strToArrayBuffer(qrImage);
+        case "PNG":
+            return qrImage.buffer;
+        default:
+            throw new OperationError("Unsupported QR code format.");
+    }
+}