图片url地址转file文件

        urlToFile = (url) => {// url是文件的url地址
            let image = new Image();
            image.src = url;
            image.onload = function () {
                let base64 = getBase64Image(image),
                    file = btof(base64, "noChange");
                    console.log(file) // 这个file就是转换成功的file文件
            };
        },
        /** url 转换成img */
        getBase64Image = (img) => {
            let canvas = document.createElement("canvas");
            canvas.width = img.width;
            canvas.height = img.height;
            let ctx = canvas.getContext("2d");
            ctx.drawImage(img, 0, 0, img.width, img.height);
            let ext = img.src.substring(img.src.lastIndexOf(".") + 1).toLowerCase(),
                dataURL = canvas.toDataURL("image/" + ext);
            return dataURL;
        },
        /** base64 转换成file */
        btof = (data, fileName) => {
            const dataArr = data.split(","),
                byteString = atob(dataArr[1]),
                options = {
                    type: "image/jpeg",
                    endings: "native"
                },
                u8Arr = new Uint8Array(byteString.length);
            for (let i = 0; i < byteString.length; i++) {
                u8Arr[i] = byteString.charCodeAt(i);
            }
            return new File([u8Arr], fileName + ".jpg", options);
        },