水印 canvas 实现

let str = info;

let c = document.createElement("canvas");

document.body.appendChild.c;

let ctx = c.getContext("2d");

ctx.font = "14px Arial";

let gradient = ctx.createLinearGradient(0, 0, c.width, 0);

gradient.addColorStop("1", "rgba(0,0,0,0.1)");

ctx.fillStyle = gradient;

ctx.setTransform(0.9, -0.4, 0.5, 1, 5, 60);

ctx.fillText(str, 0, 40);

let imgsrc = c.toDataURL("image/png");

let a = document.getElementById('box');

a.style.background = "url(" + imgsrc + ") 0/30%,url(" + imgsrc + ") 25%/30%";