Desktop: Add support for plugin imaging API (#8900)

packages/lib/services/plugins/api/JoplinImaging.ts

@@ -0,0 +1,97 @@
+/* eslint-disable multiline-comment-style */
+
+export interface Implementation {
+	nativeImage: any;
+}
+
+export interface CreateFromBufferOptions {
+	width?: number;
+	height?: number;
+	scaleFactor?: number;
+}
+
+export interface ResizeOptions {
+	width?: number;
+	height?: number;
+	quality?: 'good' | 'better' | 'best';
+}
+
+export type Handle = string;
+
+interface Image {
+	handle: Handle;
+	data: any;
+}
+
+/**
+ * Provides imaging functions to resize or process images. You create an image
+ * using one of the `createFrom` functions, then use the other functions to
+ * process the image.
+ *
+ * Images are associated with a handle which is what will be available to the
+ * plugin. Once you are done with an image, free it using the `free()` function.
+ *
+ * [View the
+ * example](https://github.com/laurent22/joplin/blob/dev/packages/app-cli/tests/support/plugins/imaging/src/index.ts)
+ *
+ */
+export default class JoplinImaging {
+
+	private implementation_: Implementation;
+	private images_: Image[] = [];
+
+	public constructor(implementation: Implementation) {
+		this.implementation_ = implementation;
+	}
+
+	private createImageHandle(): Handle {
+		return [Date.now(), Math.random()].join(':');
+	}
+
+	private imageByHandle(handle: Handle) {
+		const image = this.images_.find(i => i.handle === handle);
+		if (!image) throw new Error(`No image with handle ${handle}`);
+		return image;
+	}
+
+	private cacheImage(data: any) {
+		const handle = this.createImageHandle();
+		this.images_.push({
+			handle,
+			data,
+		});
+		return handle;
+	}
+
+	public async createFromBuffer(buffer: any, options: CreateFromBufferOptions = null): Promise<Handle> {
+		return this.cacheImage(this.implementation_.nativeImage.createFromBuffer(buffer, options));
+	}
+
+	public async resize(handle: Handle, options: ResizeOptions = null) {
+		const image = this.imageByHandle(handle);
+		const resizedImage = image.data.resize(options);
+		return this.cacheImage(resizedImage);
+	}
+
+	public async toDataUrl(handle: Handle): Promise<string> {
+		const image = this.imageByHandle(handle);
+		return image.data.toDataURL();
+	}
+
+	public async toBase64(handle: Handle) {
+		const dataUrl = await this.toDataUrl(handle);
+		const s = dataUrl.split('base64,');
+		if (s.length !== 2) throw new Error('Could not convert to base64');
+		return s[1];
+	}
+
+	/**
+	 * Image data is not automatically deleted by Joplin so make sure you call
+	 * this method on the handle once you are done.
+	 */
+	public async free(handle: Handle) {
+		const index = this.images_.findIndex(i => i.handle === handle);
+		if (index >= 0) this.images_.splice(index, 1);
+	}
+
+}