tools/image-watermark/main.ts

#!/usr/bin/env -S deno run -A

import sharp from "sharp";
import {Buffer} from "node:buffer";
import {parseArgs} from "@std/cli/parse-args";

export interface WatermarkOptions {
  /** 水印文字 */
  text: string;
  /** 字体大小 (默认 24) */
  fontSize?: number;
  /** 字体颜色 (默认白色，格式：#FFFFFF 或 rgba) */
  color?: string;
  /** 背景颜色 (默认透明，格式：#00000080 或 rgba) */
  backgroundColor?: string;
  /** 背景内边距 (默认 5) */
  backgroundPadding?: number;
  /** 距离右边距的像素 (默认 10) */
  marginRight?: number;
  /** 距离底边距的像素 (默认 10) */
  marginBottom?: number;
  /** 输出路径 (默认在原文件名后添加 _watermarked) */
  outputPath?: string;
}

function getDefaultOutputPath(inputPath: string): string {
  const lastDot = inputPath.lastIndexOf(".");
  return lastDot !== -1
    ? `${inputPath.slice(0, lastDot)}_watermarked${inputPath.slice(lastDot)}`
    : `${inputPath}_watermarked`;
}

/**
 * 在图片右下角添加文字水印
 * @param inputPath 输入图片路径
 * @param options 水印选项
 */
export async function addWatermark(
  inputPath: string,
  options: WatermarkOptions,
): Promise<void> {
  const {
    text,
    fontSize = 24,
    color = "black",
    backgroundColor,
    backgroundPadding = 5,
    marginRight = 10,
    marginBottom = 10,
  } = options;

  let outputPath = options.outputPath;
  if (!outputPath) {
    outputPath = getDefaultOutputPath(inputPath);
  }

  // 获取原图信息
  const metadata = await sharp(inputPath).metadata();
  const width = metadata.width!;
  const height = metadata.height!;

  // 估算文字宽度（使用更精确的系数，根据常见字体调整）
  // sans-serif 字体在 SVG 中的平均宽度系数约为 0.5-0.6
  const textWidth = Math.ceil(text.length * fontSize * 0.55);
  const textHeight = Math.ceil(fontSize * 0.9);

  // 背景矩形尺寸
  const bgWidth = textWidth + backgroundPadding * 2;
  const bgHeight = textHeight + backgroundPadding * 2;

  // 文字和背景位置（右下角对齐）
  // text-anchor="end" 意味着文字的右边缘在指定的 x 坐标
  const textX = width - marginRight - 20;
  const textY = height - marginBottom;

  // 背景矩形的左上角坐标
  // 背景右边缘与文字右边缘对齐
  const rectX = textX - bgWidth + 20;
  const rectY = textY - bgHeight + backgroundPadding + 2;

  // 创建最终 SVG 水印
  const svg =
    `<svg width="${width}" height="${height}" xmlns="http://www.w3.org/2000/svg">
    ${
      backgroundColor
        ? `<rect x="${rectX}" y="${rectY}" width="${bgWidth}" height="${bgHeight}" fill="${backgroundColor}" rx="4"/>`
        : ""
    }
    <text x="${textX}" y="${textY}" font-family="sans-serif" font-size="${fontSize}" fill="${color}" text-anchor="end" dominant-baseline="alphabetic">${
      escapeXml(text)
    }</text>
  </svg>`;

  // 将 SVG 水印叠加到原图
  await sharp(inputPath).composite([
    {
      input: Buffer.from(svg),
      top: 0,
      left: 0,
    },
  ])
    .toFile(outputPath);

  if (inputPath == outputPath) {
    console.log(`Added watermark: ${inputPath}`);
  } else {
    console.log(`Added watermark: ${inputPath} -> ${outputPath}`);
  }
}

/**
 * 转义 XML 特殊字符
 */
function escapeXml(str: string): string {
  return str
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
    .replace(/"/g, "&quot;")
    .replace(/'/g, "&apos;");
}

if (import.meta.main) {
  const flags = parseArgs(Deno.args, {
    boolean: ["help", "unsafe-replace-file"],
    string: ["watermark"],
  });

  const watermarkText = flags.watermark;
  const imagePaths = flags._;

  if (!watermarkText || imagePaths.length == 0) {
    console.log("Usage: deno run -A main.ts --watermark 'watermark' <FILES>");
    console.log(
      "Example: deno run -A main.ts --watermark '© 2026 MyName' image.jpg",
    );
    Deno.exit(1);
  }

  for (const imagePath of imagePaths) {
    const imagePathStr = imagePath as string;

    const options = {
      fontSize: 32,
      text: watermarkText,
      color: "black",
      backgroundPadding: 2,
      backgroundColor: "white",
    } as WatermarkOptions;
    if (flags["unsafe-replace-file"]) {
      options.outputPath = imagePathStr;
    }

    await addWatermark(imagePathStr, options);
  }
}