get google related images URL ( https://www.google.com/search?tbs=sbi: ... ) based on an image URL

getImageResultsURLFromImageURL

// notes:
// this function should be used from within the background script of a webextension
// also included are two examples at the bottom to demonstrate its use

async function getImageResultsURLFromImageURL(URL) {
  
  // input: string
  // the input is the URL of the image you want to search for 
  // it can either start with "http" or "data:" (for base64 encoded images)
  
  // output: string
  // the output is the URL of the image results (regular, not google lens)
  // the output URL starts with "https://www.google.com/search?tbs=sbi:"
  
  const lens = async (URL) => {
    // find the normal image results URL within the HTML of the Google Lens results
    const response = await fetch(URL, {
      "body": null,
      "method": "GET",
      "mode": "cors",
    })
    let body = await response.text()
    let index = body.indexOf(`https://www.google.com/search?tbs`)
    if (index === -1) {
      throw new Error("tbs prefix url not found")
    }
    body = body.substring(index, body.length)
    index = body.indexOf(`"`)
    if (index === -1) {
      throw new Error("quotation marks not found")
    }
    body = body.substring(0,index)
    body = body.replace(`\\u003d`, "=")
    if (!body.startsWith("https")) {
      throw new Error(`body does not start with https, body length is ${body.length}`)
    }
    return body
  }
  
  const get = async (URL) => {
    // find the Google Lens results URL from an HTTP/HTTPS image URL
    const encodedURL = encodeURIComponent(URL)
    const crawlRequestURL = `https://lens.google.com/uploadbyurl?url=${encodedURL}&hl=en&re=df&st=${+ new Date()}&ep=gisbubu`
    const response = await fetch(crawlRequestURL, {
      "body": null,
      "method": "GET",
      "mode": "cors",
    })
    return response.url
  }
  
  const post = async (URL) => {
    // find the Google Lens results URL from a base64 image URL
    const blob = await (await fetch(URL)).blob()
    const formData = new FormData()
    formData.append("encoded_image", blob, `${+ new Date()}.png`)
    let response = await fetch(`https://lens.google.com/upload?hl=en&re=df&st=${+ new Date()}&ep=gisbubb`, {
      "body": formData,
      "method": "POST",
      "mode": "cors"
    })
    let text = await response.text()
    if (text.indexOf("refresh") === -1) {
      throw new Error("no base64 meta refresh found")
      return null
    }
    let index = text.indexOf('https://lens.google.com')
    text = text.slice(index)
    index = text.indexOf('"')
    if (index === -1) {
      index = text.indexOf("'")
      if (index === -1) {
        throw new Error("quotation marks not found")
        return null
      }
    }
    text = text.slice(0,index)
    if (!text.startsWith("http")) {
      throw new Error("url did not start with http")
      return null
    }
    return text
  }
  
  try {
    // if no valid URL provided, return null
    if (!URL || URL.length === 0 || typeof URL !== "string") {
      return null
    }
    let redirect = null
    if (URL.startsWith("data:")) {
      // get the Google Lens URL based on a base64 image URL
      redirect = await post(URL)
    }
    else {
      // get the Google Lens URL based on an HTTP/HTTPS image URL
      redirect = await get(URL)
    }
    // return the normal image results URL
    return await lens(redirect)
  }
  catch(e) {
    console.error(e)
    if (!URL.startsWith("data:")) {
      // as a fallback, return the Google Lens results URL
      const encodedURL = URL.replaceAll("?", '%3F').replaceAll("&", '%26')
      return `https://lens.google.com/uploadbyurl?url=${encodedURL}`
    }
    else {
      // return null if a base64 image was provided and wasn't able to resolve
      return null
    }
  } 
  
};

// examples:

// get the normal image results URL from an HTTPS image URL
(async function() {
  const imageURL = "https://i.imgur.com/VcMUWBC.jpeg"
  const results = await getImageResultsURLFromImageURL(imageURL)
  console.log(results) // https://www.google.com/search?tbs=sbi:AMhZZisKeirUN5_1-_1AfP0ZUcMShmlwPs0MGTCsOcPrfqv_1ii1AY2ximpsNpO6TnEsNDa8L5Bc0hKxRecsm8wEJfgFG1K85SBAGW-K3bb0sVPuImQHW24qIIU7xfzRpHFgKl2REAScR2RGphYZDWf_1dBxVNefRmZ2GQ
})();

// get the normal image results URL from a base64 image URL
(async function() {
  const imageURL = "data:image/jpeg;base64,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"
  const results = await getImageResultsURLFromImageURL(imageURL)
  console.log(results) // https://www.google.com/search?tbs=sbi:AMhZZiuQRfow5gK0DKoShC5tjLNXDbIsFPMtCfNpUGU2NtsYLLbRE16ITRsECSMmZC8I1HmU04Cgi0--0qUci_14tkoOZAg2gisCcAOceGfFNypdlC0W5SP9hhW7qwbq-OSkd-ts49B6k5KLXfFZTC5KOsrBJiRs3HA
})();