jSignature签名后字体向左旋转90度

rotateBase64Img(dataStr, -90);//-90向左旋转90度，90向右旋转90度。

function rotateBase64Img(src, edg) {
        var canvas = document.createElement("canvas");
        var ctx = canvas.getContext("2d");
        var imgW;//图片宽度
        var imgH;//图片高度
        var size;//canvas初始大小
        if (edg % 90 != 0) {
            console.log("旋转角度必须是90的倍数!");
            throw "旋转角度必须是90的倍数!";
        }
        (edg < 0) && (edg = (edg % 360) + 360);
        const quadrant = (edg / 90) % 4; //旋转象限
        const cutCoor = {sx: 0, sy: 0, ex: 0, ey: 0}; //裁剪坐标

        var image = new Image();
        image.crossOrigin = "anonymous";
        image.src = src;
        image.onload = function () {
            imgW = image.width;
            imgH = image.height;
            size = imgW > imgH ? imgW : imgH;
            canvas.width = size * 2;
            canvas.height = size * 2;
            switch (quadrant) {
                case 0:
                    cutCoor.sx = size;
                    cutCoor.sy = size;
                    cutCoor.ex = size + imgW;
                    cutCoor.ey = size + imgH;
                    break;
                case 1:
                    cutCoor.sx = size - imgH;
                    cutCoor.sy = size;
                    cutCoor.ex = size;
                    cutCoor.ey = size + imgW;
                    break;
                case 2:
                    cutCoor.sx = size - imgW;
                    cutCoor.sy = size - imgH;
                    cutCoor.ex = size;
                    cutCoor.ey = size;
                    break;
                case 3:
                    cutCoor.sx = size;
                    cutCoor.sy = size - imgW;
                    cutCoor.ex = size + imgH;
                    cutCoor.ey = size + imgW;
                    break;
            }
            ctx.translate(size, size);
            ctx.rotate(edg * Math.PI / 180);
            ctx.drawImage(image, 0, 0);
            var imgData = ctx.getImageData(cutCoor.sx, cutCoor.sy, cutCoor.ex, cutCoor.ey);
            if (quadrant % 2 == 0) {
                canvas.width = imgW;
                canvas.height = imgH;
            } else {
                canvas.width = imgH;
                canvas.height = imgW;
            }
            ctx.putImageData(imgData, 0, 0);
            if (sign_tip == 1) {
                $('#student_sign_img').attr('src',canvas.toDataURL());
                $('#student_sign').attr('src',canvas.toDataURL());
                $('#student_sign_input').val(canvas.toDataURL());
                //$('#student_sign').hide();
            } else {
                $('#family_sign_img').attr('src',canvas.toDataURL());
                $('#family_sign').attr('src',canvas.toDataURL());
                $('#family_sign_input').val(canvas.toDataURL());
                //$('#family_sign').hide();
            }
            $('.signature_wrap').hide();
        };
    }