@gutenye/ocr-node/src/ImageRaw.ts

Guten OCR is a high accurate text detection (OCR) Javascript/Typescript library that runs on Node.js, Browser, React Native and C++. Based on PaddleOCR and ONNX runtime

import filePath from 'node:path'
import { ImageRawBase } from '@gutenye/ocr-common'
import type { ImageRawData, LineImage, SizeOption } from '@gutenye/ocr-common'
import sharp from 'sharp'

export class ImageRaw extends ImageRawBase {
  #sharp: sharp.Sharp

  static async open(path: string): Promise<ImageRaw> {
    return new ImageRaw(await toImageRaw(sharp(path).ensureAlpha(1)))
  }

  constructor(imageRawData: ImageRawData) {
    super(imageRawData)
    this.#sharp = toSharp(imageRawData)
  }

  async write(path: string) {
    const ext = filePath.extname(path).slice(1)
    return this.#sharp.toFormat(ext as keyof sharp.FormatEnum).toFile(path)
  }

  async resize(size: SizeOption) {
    return this.#apply(
      this.#sharp.resize({
        width: size.width,
        height: size.height,
        fit: 'contain',
      }),
    )
  }

  async drawBox(lineImages: LineImage[]) {
    const svg = `
      <svg width="${this.width}" height="${this.height}">
        ${lineImages
          .map((lineImage) => {
            const [p1, p2, p3, p4] = lineImage.box
            return `<polygon points="${p1[0]},${p1[1]} ${p2[0]},${p2[1]} ${p3[0]},${p3[1]} ${p4[0]},${p4[1]}"  fill="none" stroke="red" />`
          })
          .join('\n')}
      </svg>
    `
    return this.#apply(this.#sharp.composite([{ input: Buffer.from(svg), left: 0, top: 0 }]))
  }

  async #apply(sharp: sharp.Sharp) {
    this.#sharp = sharp
    const result = await toImageRaw(sharp)
    this.data = result.data
    this.width = result.width
    this.height = result.height
    return this
  }
}

async function toImageRaw(sharp: sharp.Sharp) {
  const result = await sharp.raw().toBuffer({ resolveWithObject: true })
  return {
    data: result.data,
    width: result.info.width,
    height: result.info.height,
  }
}

function toSharp(imageRawData: ImageRawData) {
  return sharp(imageRawData.data, {
    raw: {
      width: imageRawData.width,
      height: imageRawData.height,
      channels: 4,
    },
  })
}