在之前的網(wǎng)頁(yè)瀏覽器中我們可以通過長(zhǎng)按保存圖片來(lái)實(shí)現(xiàn)保存圖片等等的操作，現(xiàn)在的話就被去掉了，那么我們就來(lái)講講有關(guān)于“怎么解決在網(wǎng)頁(yè)長(zhǎng)按保存圖片問題？”這個(gè)問題吧！
下面是詳細(xì)的步驟：
1. html2canvas截屏
保存的圖片節(jié)點(diǎn)最好是img標(biāo)簽： 想要截屏的節(jié)點(diǎn)最好是img標(biāo)簽的圖片，經(jīng)測(cè)試如果是 background-image 會(huì)有點(diǎn)模糊，需要特別注意下。
npm i html2canvas --save
import html2canvas from 'html2canvas';
// 想要保存的圖片節(jié)點(diǎn)
const dom = document.querySelector('img');
// 創(chuàng)建一個(gè)新的canvas
const Canvas = document.createElement('canvas');
const width = document.body.offsetWidth; // 可見屏幕的寬
const height = document.body.offsetHeight; // 可見屏幕的高
const scale = window.devicePixelRadio; // 設(shè)備的devicePixelRadio
// 將Canvas畫布放大scale倍，然后放在小的屏幕里，解決模糊問題
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');
// 關(guān)閉抗鋸齒形
context.mozImageSmoothingEnabled = false;
context.webkitImageSmoothingEnabled = false;
context.msImageSmoothingEnabled = false;
context.imageSmoothingEnabled = false;
// canvas轉(zhuǎn)化為圖片
canvas2Image(canvas, canvas.width, canvas.height);
});2. canvas2Image轉(zhuǎn)化為圖片
一般情況下轉(zhuǎn)為jpeg格式就很不錯(cuò)了。
canvas2Image(canvas, canvas.width, canvas.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'); // 可以根據(jù)需要更改格式
return img;
}3. 長(zhǎng)按保存圖片
先實(shí)現(xiàn)一個(gè)長(zhǎng)按的方法，長(zhǎng)按之后把生成的圖片append到body，透明浮在屏幕上。
// 封裝一個(gè)長(zhǎng)按方法
longPress(fn) {
let timeout = 0;
const $this = this;
for (let i = 0; i < $this.length; i++) {
$this[i].addEventListener('touchstart', () => {
timeout = setTimeout(fn, 800); // 長(zhǎng)按時(shí)間超過800ms，則執(zhí)行傳入的方法
}, false);
$this[i].addEventListener('touchend', () => {
clearTimeout(timeout); // 長(zhǎng)按時(shí)間少于800ms，不會(huì)執(zhí)行傳入的方法
}, false);
}
}
// 添加生成的圖片到body
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;";4. 完整代碼如下：
$.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); // 長(zhǎng)按時(shí)間超過800ms，則執(zhí)行傳入的方法
}, false);
$this[i].addEventListener('touchend', () => {
clearTimeout(timeout); // 長(zhǎng)按時(shí)間少于800ms，不會(huì)執(zhí)行傳入的方法
}, false);
}
};
$('img').longPress(() => {
saveImg();
});saveImg() {
// 想要保存的圖片節(jié)點(diǎn)
const dom = document.querySelector('img');
// 創(chuàng)建一個(gè)新的canvas
const Canvas = document.createElement('canvas');
const width = document.body.offsetWidth; // 可見屏幕的寬
const height = document.body.offsetHeight; // 可見屏幕的高
const scale = window.devicePixelRatio; // 設(shè)備的devicePixelRatio
// 將Canvas畫布放大scale倍，然后放在小的屏幕里，解決模糊問題
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');
// 關(guān)閉抗鋸齒形
context.mozImageSmoothingEnabled = false;
context.webkitImageSmoothingEnabled = false;
context.msImageSmoothingEnabled = false;
context.imageSmoothingEnabled = false;
// canvas轉(zhuǎn)化為圖片
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'); // 可以根據(jù)需要更改格式
return img;
}剛開始做的時(shí)候也是網(wǎng)上一堆文章亂看，不斷的試錯(cuò)，最后愉快的實(shí)現(xiàn)了長(zhǎng)按保存圖片的功能，做完才發(fā)現(xiàn)也很簡(jiǎn)單哈，這篇文章完整的介紹了整個(gè)流程，拿走不謝！
總結(jié)
那么以上所述的就是今天小編給大家介紹的有關(guān)于“怎么解決在網(wǎng)頁(yè)長(zhǎng)按保存圖片問題？”這方面的相關(guān)內(nèi)容分享！更多的相關(guān)內(nèi)容都可以在W3Cschool中進(jìn)行學(xué)習(xí)！
