$.fn.longPress = function(fn) {

let timeout = 0;

const $this = this;

for (let i = 0; i < $this.length; i++) {

$this[i].addEventListener('touchstart', () => {

timeout = setTimeout(fn, 800); // 长按时间超过800ms，则执行传入的方法

}, false);

$this[i].addEventListener('touchend', () => {

clearTimeout(timeout); // 长按时间少于800ms，不会执行传入的方法

}, false);

}

};

$('img').longPress(() => {

saveImg();

});saveImg() {

// 想要保存的图片节点

const dom = document.querySelector('img');

// 创建一个新的canvas

const Canvas = document.createElement('canvas');

const width = document.body.offsetWidth; // 可见屏幕的宽

const height = document.body.offsetHeight; // 可见屏幕的高

const scale = window.devicePixelRatio; // 设备的devicePixelRatio

// 将Canvas画布放大scale倍，然后放在小的屏幕里，解决模糊问题

Canvas.width = width * scale;

Canvas.height = height * scale;

Canvas.getContext('2d').scale(scale, scale);

html2canvas(dom, {

canvas: Canvas,

scale,

useCORS: true,

logging: true,

width: width + 'px',

hegiht: height + 'px',

}).then((canvas) => {

const context = canvas.getContext('2d');

// 关闭抗锯齿形

context.mozImageSmoothingEnabled = false;

context.webkitImageSmoothingEnabled = false;

context.msImageSmoothingEnabled = false;

context.imageSmoothingEnabled = false;

// canvas转化为图片

const img = canvas2Image(canvas, canvas.width, canvas.height);

document.body.appendChild(img);

img.style.cssText = "width:100%;height:100%;position:absolute;top:0;left:0;right:0;bottom:0;opacity:0;";

}

}

canvas2Image(canvas, width, height) {

const retCanvas = document.createElement('canvas');

const retCtx = retCanvas.getContext('2d');

retCanvas.width = width;

retCanvas.height = height;

retCtx.drawImage(canvas, 0, 0, width, height, 0, 0, width, height);

const img = document.createElement('img');

img.src = retCanvas.toDataURL('image/jpeg'); // 可以根据需要更改格式

return img;

}