Google 的“报告错误”或“反馈工具”可让您选择浏览器窗口的一个区域来创建屏幕截图，并提交您对错误的反馈。
Jason Small 的屏幕截图，发布在重复的问题中。
他们是怎么做到的？Google 的 JavaScript 反馈 API 从这里加载，他们对反馈模块的概述将展示截图功能。
问问题
582520 次
7 回答
1238
JavaScript 可以读取 DOM 并使用canvas. 我一直在研究将 HTML 转换为画布图像的脚本。今天决定将其实施为发送您所描述的反馈。
该脚本允许您创建反馈表单，其中包括在客户端浏览器上创建的屏幕截图以及表单。屏幕截图基于 DOM，因此可能不是 100% 准确到真实表示，因为它不会制作实际的屏幕截图，而是根据页面上可用的信息构建屏幕截图。
它不需要来自服务器的任何渲染，因为整个图像是在客户端的浏览器上创建的。HTML2Canvas 脚本本身仍处于非常实验性的状态，因为它几乎无法解析我希望它解析的 CSS3 属性，即使代理可用，它也不支持加载 CORS 图像。
仍然相当有限的浏览器兼容性（不是因为无法支持更多，只是没有时间让它更多地支持跨浏览器）。
有关更多信息，请查看此处的示例：
http://hertzen.com/experiments/jsfeedback/
编辑 html2canvas 脚本现在可在此处单独使用，并在此处提供一些示例。
编辑 2 Google 反馈团队的 Elliott Sprehn 的此演示文稿中可以找到 Google 使用非常相似的方法的另一个确认（事实上，基于文档，唯一的主要区别是它们的异步遍历/绘图方法）： http： //www.elliottsprehn.com/preso/fluentconf/
于 2011-07-13T11:29:53.443 回答
80
您的 Web 应用程序现在可以使用以下命令对客户端的整个桌面进行“本机”屏幕截图getUserMedia()：
看看这个例子：
https://www.webrtc-experiment.com/Pluginfree-Screen-Sharing/
客户端必须使用 chrome（目前），并且需要在 chrome://flags 下启用屏幕捕获支持。
于 2013-10-29T09:33:09.947 回答
53
概念验证
正如Niklas 提到的，您可以使用html2canvas库在浏览器中使用 JS 截取屏幕截图。在这一点上，我将通过提供一个使用此库截取屏幕截图的示例（“概念证明”）来扩展他的答案：
function report() {
let region = document.querySelector("body"); // whole screen
html2canvas(region, {
onrendered: function(canvas) {
let pngUrl = canvas.toDataURL(); // png in dataURL format
let img = document.querySelector(".screen");
img.src = pngUrl;
// here you can allow user to set bug-region
// and send it with 'pngUrl' to server
},
});
}.container {
margin-top: 10px;
border: solid 1px black;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.min.js"></script>
<div>Screenshot tester</div>
<button onclick="report()">Take screenshot</button>
<div class="container">
<img width="75%" class="screen">
</div>在获取图像作为数据URI后的report()功能中onrendered，您可以将其显示给用户并允许他通过鼠标绘制“错误区域”，然后将屏幕截图和区域坐标发送到服务器。
在这个例子 async/await中，版本是：with nice makeScreenshot()function 。
更新
一个简单的例子，它允许你截屏、选择区域、描述错误和发送 POST 请求（这里是 jsfiddle）（主要功能是report()）。
async function report() {
let screenshot = await makeScreenshot(); // png dataUrl
let img = q(".screen");
img.src = screenshot;
let c = q(".bug-container");
c.classList.remove('hide')
let box = await getBox();
c.classList.add('hide');
send(screenshot,box); // sed post request with bug image, region and description
alert('To see POST requset with image go to: chrome console > network tab');
}
// ----- Helper functions
let q = s => document.querySelector(s); // query selector helper
window.report = report; // bind report be visible in fiddle html
async function makeScreenshot(selector="body")
{
return new Promise((resolve, reject) => {
let node = document.querySelector(selector);
html2canvas(node, { onrendered: (canvas) => {
let pngUrl = canvas.toDataURL();
resolve(pngUrl);
}});
});
}
async function getBox(box) {
return new Promise((resolve, reject) => {
let b = q(".bug");
let r = q(".region");
let scr = q(".screen");
let send = q(".send");
let start=0;
let sx,sy,ex,ey=-1;
r.style.width=0;
r.style.height=0;
let drawBox= () => {
r.style.left = (ex > 0 ? sx : sx+ex ) +'px';
r.style.top = (ey > 0 ? sy : sy+ey) +'px';
r.style.width = Math.abs(ex) +'px';
r.style.height = Math.abs(ey) +'px';
}
//console.log({b,r, scr});
b.addEventListener("click", e=>{
if(start==0) {
sx=e.pageX;
sy=e.pageY;
ex=0;
ey=0;
drawBox();
}
start=(start+1)%3;
});
b.addEventListener("mousemove", e=>{
//console.log(e)
if(start==1) {
ex=e.pageX-sx;
ey=e.pageY-sy
drawBox();
}
});
send.addEventListener("click", e=>{
start=0;
let a=100/75 //zoom out img 75%
resolve({
x:Math.floor(((ex > 0 ? sx : sx+ex )-scr.offsetLeft)*a),
y:Math.floor(((ey > 0 ? sy : sy+ey )-b.offsetTop)*a),
width:Math.floor(Math.abs(ex)*a),
height:Math.floor(Math.abs(ex)*a),
desc: q('.bug-desc').value
});
});
});
}
function send(image,box) {
let formData = new FormData();
let req = new XMLHttpRequest();
formData.append("box", JSON.stringify(box));
formData.append("screenshot", image);
req.open("POST", '/upload/screenshot');
req.send(formData);
}.bug-container { background: rgb(255,0,0,0.1); margin-top:20px; text-align: center; }
.send { border-radius:5px; padding:10px; background: green; cursor: pointer; }
.region { position: absolute; background: rgba(255,0,0,0.4); }
.example { height: 100px; background: yellow; }
.bug { margin-top: 10px; cursor: crosshair; }
.hide { display: none; }
.screen { pointer-events: none }<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.min.js"></script>
<body>
<div>Screenshot tester</div>
<button onclick="report()">Report bug</button>
<div class="example">Lorem ipsum</div>
<div class="bug-container hide">
<div>Select bug region: click once - move mouse - click again</div>
<div class="bug">
<img width="75%" class="screen" >
<div class="region"></div>
</div>
<div>
<textarea class="bug-desc">Describe bug here...</textarea>
</div>
<div class="send">SEND BUG</div>
</div>
</body>于 2018-07-01T19:25:09.210 回答
47
使用getDisplayMedia API以 Canvas 或 Jpeg Blob / ArrayBuffer 形式获取屏幕截图：
修复 1：仅将 getUserMedia 与 chromeMediaSource 用于 Electron.js
修复 2：抛出错误而不是返回空对象
修复 3：修复演示以防止错误：getDisplayMedia must be called from a user gesture handler
// docs: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia
// see: https://www.webrtc-experiment.com/Pluginfree-Screen-Sharing/#20893521368186473
// see: https://github.com/muaz-khan/WebRTC-Experiment/blob/master/Pluginfree-Screen-Sharing/conference.js
function getDisplayMedia(options) {
if (navigator.mediaDevices && navigator.mediaDevices.getDisplayMedia) {
return navigator.mediaDevices.getDisplayMedia(options)
}
if (navigator.getDisplayMedia) {
return navigator.getDisplayMedia(options)
}
if (navigator.webkitGetDisplayMedia) {
return navigator.webkitGetDisplayMedia(options)
}
if (navigator.mozGetDisplayMedia) {
return navigator.mozGetDisplayMedia(options)
}
throw new Error('getDisplayMedia is not defined')
}
function getUserMedia(options) {
if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
return navigator.mediaDevices.getUserMedia(options)
}
if (navigator.getUserMedia) {
return navigator.getUserMedia(options)
}
if (navigator.webkitGetUserMedia) {
return navigator.webkitGetUserMedia(options)
}
if (navigator.mozGetUserMedia) {
return navigator.mozGetUserMedia(options)
}
throw new Error('getUserMedia is not defined')
}
async function takeScreenshotStream() {
// see: https://developer.mozilla.org/en-US/docs/Web/API/Window/screen
const width = screen.width * (window.devicePixelRatio || 1)
const height = screen.height * (window.devicePixelRatio || 1)
const errors = []
let stream
try {
stream = await getDisplayMedia({
audio: false,
// see: https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamConstraints/video
video: {
width,
height,
frameRate: 1,
},
})
} catch (ex) {
errors.push(ex)
}
// for electron js
if (navigator.userAgent.indexOf('Electron') >= 0) {
try {
stream = await getUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
// chromeMediaSourceId: source.id,
minWidth : width,
maxWidth : width,
minHeight : height,
maxHeight : height,
},
},
})
} catch (ex) {
errors.push(ex)
}
}
if (errors.length) {
console.debug(...errors)
if (!stream) {
throw errors[errors.length - 1]
}
}
return stream
}
async function takeScreenshotCanvas() {
const stream = await takeScreenshotStream()
// from: https://stackoverflow.com/a/57665309/5221762
const video = document.createElement('video')
const result = await new Promise((resolve, reject) => {
video.onloadedmetadata = () => {
video.play()
video.pause()
// from: https://github.com/kasprownik/electron-screencapture/blob/master/index.js
const canvas = document.createElement('canvas')
canvas.width = video.videoWidth
canvas.height = video.videoHeight
const context = canvas.getContext('2d')
// see: https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement
context.drawImage(video, 0, 0, video.videoWidth, video.videoHeight)
resolve(canvas)
}
video.srcObject = stream
})
stream.getTracks().forEach(function (track) {
track.stop()
})
if (result == null) {
throw new Error('Cannot take canvas screenshot')
}
return result
}
// from: https://stackoverflow.com/a/46182044/5221762
function getJpegBlob(canvas) {
return new Promise((resolve, reject) => {
// docs: https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob
canvas.toBlob(blob => resolve(blob), 'image/jpeg', 0.95)
})
}
async function getJpegBytes(canvas) {
const blob = await getJpegBlob(canvas)
return new Promise((resolve, reject) => {
const fileReader = new FileReader()
fileReader.addEventListener('loadend', function () {
if (this.error) {
reject(this.error)
return
}
resolve(this.result)
})
fileReader.readAsArrayBuffer(blob)
})
}
async function takeScreenshotJpegBlob() {
const canvas = await takeScreenshotCanvas()
return getJpegBlob(canvas)
}
async function takeScreenshotJpegBytes() {
const canvas = await takeScreenshotCanvas()
return getJpegBytes(canvas)
}
function blobToCanvas(blob, maxWidth, maxHeight) {
return new Promise((resolve, reject) => {
const img = new Image()
img.onload = function () {
const canvas = document.createElement('canvas')
const scale = Math.min(
1,
maxWidth ? maxWidth / img.width : 1,
maxHeight ? maxHeight / img.height : 1,
)
canvas.width = img.width * scale
canvas.height = img.height * scale
const ctx = canvas.getContext('2d')
ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, canvas.width, canvas.height)
resolve(canvas)
}
img.onerror = () => {
reject(new Error('Error load blob to Image'))
}
img.src = URL.createObjectURL(blob)
})
}
演示：
document.body.onclick = async () => {
// take the screenshot
var screenshotJpegBlob = await takeScreenshotJpegBlob()
// show preview with max size 300 x 300 px
var previewCanvas = await blobToCanvas(screenshotJpegBlob, 300, 300)
previewCanvas.style.position = 'fixed'
document.body.appendChild(previewCanvas)
// send it to the server
var formdata = new FormData()
formdata.append("screenshot", screenshotJpegBlob)
await fetch('https://your-web-site.com/', {
method: 'POST',
body: formdata,
'Content-Type' : "multipart/form-data",
})
}
// and click on the page
于 2020-02-14T18:41:28.183 回答
16
这是一个完整的屏幕截图示例，适用于 2021 年的 chrome。最终结果是一个可以传输的 blob。流程是：请求媒体 > 抓取框架 > 绘制到画布 > 传输到 blob。如果您想提高内存效率，请探索OffscreenCanvas或ImageBitmapRenderingContext
https://jsfiddle.net/v24hyd3q/1/
// Request media
navigator.mediaDevices.getDisplayMedia().then(stream =>
{
// Grab frame from stream
let track = stream.getVideoTracks()[0];
let capture = new ImageCapture(track);
capture.grabFrame().then(bitmap =>
{
// Stop sharing
track.stop();
// Draw the bitmap to canvas
canvas.width = bitmap.width;
canvas.height = bitmap.height;
canvas.getContext('2d').drawImage(bitmap, 0, 0);
// Grab blob from canvas
canvas.toBlob(blob => {
// Do things with blob here
console.log('output blob:', blob);
});
});
})
.catch(e => console.log(e));
于 2021-02-03T13:53:51.703 回答
14
下面是一个使用示例：getDisplayMedia
document.body.innerHTML = '<video style="width: 100%; height: 100%; border: 1px black solid;"/>';
navigator.mediaDevices.getDisplayMedia()
.then( mediaStream => {
const video = document.querySelector('video');
video.srcObject = mediaStream;
video.onloadedmetadata = e => {
video.play();
video.pause();
};
})
.catch( err => console.log(`${err.name}: ${err.message}`));
同样值得一试的是Screen Capture API文档。
于 2019-08-26T21:42:44.923 回答
0
你可以试试我的新 JS 库：screenshot.js。
它可以拍摄真实的截图。
您加载脚本：
<script src="https://raw.githubusercontent.com/amiad/screenshot.js/master/screenshot.js"></script>
并截图：
new Screenshot({success: img => {
// callback function
myimage = img;
}});
您可以在项目页面中阅读更多选项。
于 2022-02-06T11:08:18.013 回答