Add dither image operation

src/core/operations/DitherImage.mjs

@@ -0,0 +1,89 @@
+/**
+ * @author j433866 [j433866@gmail.com]
+ * @copyright Crown Copyright 2019
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import OperationError from "../errors/OperationError";
+import Magic from "../lib/Magic";
+import { toBase64 } from "../lib/Base64";
+import jimp from "jimp";
+
+/**
+ * Image Dither operation
+ */
+class DitherImage extends Operation {
+
+    /**
+     * DitherImage constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Dither Image";
+        this.module = "Image";
+        this.description = "Apply a dither effect to an image.";
+        this.infoURL = "https://wikipedia.org/wiki/Dither";
+        this.inputType = "byteArray";
+        this.outputType = "byteArray";
+        this.presentType = "html";
+        this.args = [];
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {byteArray}
+     */
+    run(input, args) {
+        const type = Magic.magicFileType(input);
+
+        if (type && type.mime.indexOf("image") === 0){
+            return new Promise((resolve, reject) => {
+                jimp.read(Buffer.from(input))
+                    .then(image => {
+                        image
+                            .dither565()
+                            .getBuffer(jimp.AUTO, (error, result) => {
+                                if (error){
+                                    reject(new OperationError("Error getting the new image buffer"));
+                                } else {
+                                    resolve([...result]);
+                                }
+                            });
+                    })
+                    .catch(err => {
+                        reject(new OperationError("Error applying a dither effect to the image."));
+                    });
+            });
+        } else {
+            throw new OperationError("Invalid file type.");
+        }
+    }
+
+    /**
+     * Displays the dithered image using HTML for web apps
+     * 
+     * @param {byteArray} data
+     * @returns {html}
+     */
+    present(data) {
+        if (!data.length) return "";
+
+        let dataURI = "data:";
+        const type = Magic.magicFileType(data);
+        if (type && type.mime.indexOf("image") === 0){
+            dataURI += type.mime + ";";
+        } else {
+            throw new OperationError("Invalid file type.");
+        }
+        dataURI += "base64," + toBase64(data);
+
+        return "<img src='" + dataURI + "'>";
+
+    }
+
+}
+
+export default DitherImage;