油猴 Javascript 脚本如何调用百度 OCR 接口获取 access_token？

通过 toDataURL，将图片转化为 base64，结果为 dataUrl，去掉编码头 data:image/jpeg;base64, 进行 urlencode，然后使用 GM_xmlhttpRequest 进行 https 请求，提示 json 未定义，如何获取 access_token，以及如何输出最后识别的文字结果？

https://ai.baidu.com/ai-doc/REFERENCE/Ck3dwjhhu

toDataURL( 'https://i.imgur.com/GniA3wQ.png', function(dataUrl) { const base64Data = dataUrl.split(';base64,')[1]; var API_Key="xxxxxxxxxxxxxxxxxxxxxxxx"; var Secret_Key="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; //access_token 获取地址。 var getTokenUrl="https://aip.baidubce.com/oauth/2.0/token"; var token_Res = GM_xmlhttpRequest({ method: "POST", url: getTokenUrl, grant_type: "client_credentials", client_id: API_Key, client_secret: Secret_Key, onload: function(response){ console.log("请求成功"); console.log(response.responseText); }, onerror: function(response){ console.log("请求失败"); } }); var access_token = token_Res.body.json().access_token;//提示 json 未定义 //通用文字识别，50000 次 /天免费 var ocrUrl = "https://aip.baidubce.com/rest/2.0/ocr/v1/general_basic"; var ocr_Res = GM_xmlhttpRequest({ method: "POST", headers: { "Content-Type": "application/x-www-form-urlencoded" }, access_token: access_token, image: "image64=" + encodeURIComponent (base64Data), language_type:"CHN_ENG", //data: dataUrl, onload: function(response){ console.log("请求成功"); console.log(response.responseText); }, onerror: function(response){ console.log("请求失败"); } }); var json = ocr_Res.body.json(); console.log(json); } 

img 转化 base64

function toDataURL(src, callback, outputFormat) { var img = new Image(); //img.crossOrigin = 'Anonymous'; img.crossOrigin = ""; img.Onload= function() { var canvas = document.createElement('CANVAS'); var ctx = canvas.getContext('2d'); var dataURL; canvas.height = this.naturalHeight; canvas.width = this.naturalWidth; ctx.drawImage(this, 0, 0); dataURL = canvas.toDataURL(outputFormat); callback(dataURL); }; img.src = src; if (img.complete || img.complete === undefined) { img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw=="; img.src = src; } }