DataSource interface, ImageLoader class and test

Author: s1hofmann

lib/provider/opencv/data-source.interface.ts

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+/**
+ * A DataSource should provide methods to load data
+ *
+ * @interface DataSource
+ */
+export interface DataSource {
+  /**
+   * load will load image data from disk
+   * @param path Absolute path to output file
+   */
+  load(path: string): Promise<any>;
+}

lib/provider/opencv/image-loader.class.spec.ts

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+import * as path from "path";
+import { ImageLoader } from "./image-loader.class";
+
+describe("Image loader", () => {
+  it("should resolve to a non-empty Mat on successful load", async () => {
+    // GIVEN
+    const SUT = new ImageLoader();
+    const imagePath = path.resolve(__dirname, "./__mocks__/mouse.png");
+
+    // WHEN
+    const result = await SUT.load(imagePath);
+
+    // THEN
+    expect(result.height).toBeGreaterThan(0);
+    expect(result.width).toBeGreaterThan(0);
+  });
+
+  it("loadImage should reject on unsuccessful load", async () => {
+    // GIVEN
+    const SUT = new ImageLoader();
+    const imagePath = "./__mocks__/foo.png";
+
+    // WHEN
+    const call = SUT.load;
+
+    // THEN
+    await expect(call(imagePath)).rejects.toEqual(`Failed to load image from '${imagePath}'`);
+  });
+});

lib/provider/opencv/image-loader.class.ts

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+import * as cv from "opencv4nodejs";
+import { Image } from "../../image.class";
+import { DataSource } from "./data-source.interface";
+
+export class ImageLoader implements DataSource {
+  public async load(path: string): Promise<Image> {
+    return new Promise<Image>(async (resolve, reject) => {
+      try {
+        const image = await cv.imreadAsync(path);
+        resolve(new Image(image.cols, image.rows, image.getData(), image.channels));
+      } catch (e) {
+        reject(`Failed to load image from '${path}'`);
+      }
+    });
+  }
+}