还尝试设置图像的宽度和高度（无论如何，似乎没有关于addImage的文档）：

Try setting the width and height of the image as well (in any case, there is little documentation for addImage it seems):

var pdf = new jsPDF("l", "mm", "a4");
var imgData = canvas.toDataURL('image/jpeg', 1.0);

// due to lack of documentation; try setting w/h based on unit
pdf.addImage(imgData, 'JPEG', 10, 10, 180, 150);  // 180x150 mm @ (10,10)mm