[Image resize] #imagemagick #resize #spawn #convert

resize.ts

import { spawn } from "node:child_process";
import type { Readable } from "node:stream";

export interface ImageResizeOptions {
  quality?: number;
  square?: boolean;
}

const CONVERT_ERR_MATCH_REGEX = /convert:\s(.+)\s`/gm;

const readStreamToBuffer = async (stream: Readable) => {
  const chunks = [];

  for await (const chunk of stream) {
    chunks.push(chunk);
  }

  const buffer = Buffer.concat(chunks);

  return buffer;
};

/**
 * Меняет размер изображения
 *
 * @param jpgStream Readable поток тела изображения
 * @param maxSize Максимальная длина в пикселях наибольшей стороны изображения
 * @param options Опции
 * @returns Буфер с изображением
 * @link https://www.smashingmagazine.com/2015/06/efficient-image-resizing-with-imagemagick/
 */
export async function resizeImage(
  jpgStream: Readable,
  maxSize: number,
  options: ImageResizeOptions = {}
) {
  const { quality = 82, square = false } = options;

  /* prettier-ignore */
  const convert = spawn(
    'convert',
    [
      // Input from stream
      '-',

      // Resize
      '-thumbnail', `${maxSize}x${maxSize}>`,
      '-unsharp', '0.25x0.25+8+0.065',
      // '-dither', 'None',
      // '-posterize', '136',
      '-quality', `${quality}`,
      '-define', 'jpeg:fancy-upsampling=off',
      // '-define', 'png:compression-filter=5',
      // '-define', 'png:compression-level=9',
      // '-define', 'png:compression-strategy=1',
      // '-define', 'png:exclude-chunk=all',
      '-interlace', 'none',
      '-colorspace', 'sRGB',

      // Make canvas square
      ...(
        square
          ? [
            '-gravity', 'center',
            '-background', 'white',
            '-extent', `${maxSize}x${maxSize}`
          ]
          : []
      ),

      '-strip',

      // Output to stream
      'jpg:-'
    ],
    {
      // https://nodejs.org/api/child_process.html#optionsstdio
      // [stdin, stdout, stderr]
      stdio: ['pipe', 'pipe', 'pipe']
    }
  )

  jpgStream.pipe(convert.stdin!);

  const [imageBuffer, errBuffer] = await Promise.all([
    readStreamToBuffer(convert.stdout),
    readStreamToBuffer(convert.stderr),
  ]);

  if (errBuffer.length === 0 && imageBuffer.length) {
    return imageBuffer;
  } else {
    // convert: no decode delegate for this image format `' @ error/constitute.c/ReadImage/746.
    // convert: no images defined `jpg:-' @ error/convert.c/ConvertImageCommand/3342./
    const errorMsg = errBuffer.toString("utf8");

    let errors;

    if (errorMsg) {
      errors = [...errorMsg.matchAll(CONVERT_ERR_MATCH_REGEX)]
        .map((m) => m[1])
        .join(" | ");
    }

    throw new Error("Image resize error" + (errors ? ` - ${errors}` : ""));
  }
}