server/classes/media/preprocessors/blurhash.ts

import { encode } from "blurhash";
import sharp from "sharp";
import type { MediaPreprocessor } from "./media-preprocessor";

export class BlurhashPreprocessor implements MediaPreprocessor {
    public async process(
        file: File,
    ): Promise<{ file: File; blurhash: string | null }> {
        try {
            const arrayBuffer = await file.arrayBuffer();
            const metadata = await sharp(arrayBuffer).metadata();

            const blurhash = await new Promise<string | null>((resolve) => {
                (async () =>
                    sharp(arrayBuffer)
                        .raw()
                        .ensureAlpha()
                        .toBuffer((err, buffer) => {
                            if (err) {
                                resolve(null);
                                return;
                            }

                            try {
                                resolve(
                                    encode(
                                        new Uint8ClampedArray(buffer),
                                        metadata?.width ?? 0,
                                        metadata?.height ?? 0,
                                        4,
                                        4,
                                    ) as string,
                                );
                            } catch {
                                resolve(null);
                            }
                        }))();
            });

            return { file, blurhash };
        } catch {
            return { file, blurhash: null };
        }
    }
}