圖片轉(zhuǎn)成base64

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/**
 * 蔣圖片轉(zhuǎn)成base64
 * width、height調(diào)用時傳入具體像素值，控制大小 ,不傳則默認圖像大小
 * 可以會有跨域問題，建議是同源
 * @param imgSrc 圖片地址
 * @param width 
 * @param height
 * @returns {string}
 */
function getBase64Image(imgSrc, width, height) {
    return new Promise((resolve) => {
        const newImg = new Image();
        newImg.setAttribute('crossOrigin', 'anonymous');
        newImg.src = imgSrc;
        const canvas = document.createElement('canvas');
        canvas.width = width || img.width;
        canvas.height = height || img.height;
        const ctx = canvas.getContext('2d');
        newImg.onload = function () {
            ctx.drawImage(newImg, 0, 0, canvas.width, canvas.height);
            const dataURL = canvas.toDataURL('image/png', 1);
            resolve(dataURL);
        };
    });
}