Use original images URLs in Gmail

rewrite-gmail-img-src.js

const REGEX = /https:\/\/.*\.googleusercontent\.com\/.*#(https?:\/\/.*)/i;

// Rewrite img source on <img> tags
Array.from(
  document.querySelectorAll('img')
).forEach(img => {
  const match = img.src.match(REGEX);
  
  if (!match) {
    return;
  }

  const [, originalURL] = match;

  img.src = originalURL;
});

// Rewrite img source on CSS backgrounds
Array.from(
  document.querySelectorAll('[style]')
).forEach(element => {
  if (!element.style.backgroundImage && !element.style.background) {
    return;
  }

  let match;
  let fromBackground = false;
  let fromBackgroundImage = false;

  if (element.style.backgroundImage) {
    match = element.style.backgroundImage.match(REGEX);
    fromBackgroundImage = true;
  }

  if (!match) {
    match = element.style.background.match(REGEX);
    fromBackground = true;
  }

  if (!match) {
    return;
  }

  const [input, originalURL] = match;

  if (fromBackgroundImage) {
    element.style.backgroundImage = element.style.backgroundImage
      .replace(input, originalURL);
  }

  if (fromBackground) {
    element.style.background = element.style.background
      .replace(input, originalURL);
  }
});