使用html2canvas如何将屏幕截图保存到对象？我一直在探索演示，并看到生成屏幕截图的功能生成如下：
$(window).ready(function() {
('body').html2canvas();
});
我尝试过的是
$(window).ready(function() {
canvasRecord = $('body').html2canvas();
dataURL = canvasRecord.toDataURL("image/png");
dataURL = dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
upload(dataURL);
});
然后，我将其传递给我的upload()函数。我遇到的问题是，我无法弄清楚html2canvas()库中截图的位置或者返回它的函数。我尝试使用来自SO的this回答转换画布对象（虽然我不确定我是否需要这样做）。
我刚刚问question如何将文件上传到imgur，那里的答案（尤其是@bebraw）帮助我了解我需要做什么。
upload()函数来自Imgur示例api help：
function upload(file) {
// file is from a <input> tag or from Drag'n Drop
// Is the file an image?
if (!file || !file.type.match(/image.*/)) return;
// It is!
// Let's build a FormData object
var fd = new FormData();
fd.append("image", file); // Append the file
fd.append("key", "mykey"); // Get your own key: http://api.imgur.com/
// Create the XHR (Cross-Domain XHR FTW!!!)
var xhr = new XMLHttpRequest();
xhr.open("POST", "http://api.imgur.com/2/upload.json"); // Boooom!
xhr.onload = function() {
// Big win!
// The URL of the image is:
JSON.parse(xhr.responseText).upload.links.imgur_page;
}
// Ok, I don't handle the errors. An exercice for the reader.
// And now, we send the formdata
xhr.send(fd);
}
答案 0 :(得分：7)
我已经从this answer修改并注释了该方法。它只发送一个具有给定名称的文件，该文件由<canvas>元素组成。
if (!('sendAsBinary' in XMLHttpRequest.prototype)) {
XMLHttpRequest.prototype.sendAsBinary = function(string) {
var bytes = Array.prototype.map.call(string, function(c) {
return c.charCodeAt(0) & 0xff;
});
this.send(new Uint8Array(bytes).buffer);
};
}
/*
* @description Uploads a file via multipart/form-data, via a Canvas elt
* @param url String: Url to post the data
* @param name String: name of form element
* @param fn String: Name of file
* @param canvas HTMLCanvasElement: The canvas element.
* @param type String: Content-Type, eg image/png
***/
function postCanvasToURL(url, name, fn, canvas, type) {
var data = canvas.toDataURL(type);
data = data.replace('data:' + type + ';base64,', '');
var xhr = new XMLHttpRequest();
xhr.open('POST', url, true);
var boundary = 'ohaiimaboundary';
xhr.setRequestHeader(
'Content-Type', 'multipart/form-data; boundary=' + boundary);
xhr.sendAsBinary([
'--' + boundary,
'Content-Disposition: form-data; name="' + name + '"; filename="' + fn + '"',
'Content-Type: ' + type,
'',
atob(data),
'--' + boundary + '--'
].join('\r\n'));
}
答案 1 :(得分：2)
此代码适用于我。它会生成html2canvas的截图，将截图上传到imgur api，然后返回imgur url。
<button class="upload" >Upload to Imgur</button>
<script>
$(".upload").on("click", function(event) {
html2canvas($('body'), {
onrendered: function(canvas) {
document.body.appendChild(canvas);
try {
var img = canvas.toDataURL('image/jpeg', 0.9).split(',')[1];
} catch(e) {
var img = canvas.toDataURL().split(',')[1];
}
// open the popup in the click handler so it will not be blocked
var w = window.open();
w.document.write('Uploading...');
// upload to imgur using jquery/CORS
// https://developer.mozilla.org/En/HTTP_access_control
$.ajax({
url: 'http://api.imgur.com/2/upload.json',
type: 'POST',
data: {
type: 'base64',
// get your key here, quick and fast http://imgur.com/register/api_anon
key: 'your api key',
name: 'neon.jpg',
title: 'test title',
caption: 'test caption',
image: img
},
dataType: 'json'
}).success(function(data) {
w.location.href = data['upload']['links']['imgur_page'];
}).error(function() {
alert('Could not reach api.imgur.com. Sorry :(');
w.close();
});
},
});
});
</script>
答案 2 :(得分：1)
//Here I am using html2Canvas to capture screen and Java websockets to transfer data to server
//Limitation:Supported on latest browsers and Tomcat
Step1)Client Side : webSock.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<!-- Arun HTML File -->>
<html>
<head>
<meta charset="utf-8">
<title>Tomcat web socket</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.js"></script>
<script type="text/javascript" src="html2canvas.js?rev032"></script>
<script type="text/javascript">
var ws = new WebSocket("ws://localhost:8080/WebSocketSample/wsocket");
ws.onopen = function () {
console.log("Web Socket Open");
};
ws.onmessage = function(message) {
console.log("MSG from Server :"+message.data);
//document.getElementById("msgArea").textContent += message.data + "\n";
document.getElementById("msgArea").textContent +" Data Send\n";
};
function postToServerNew(data) {
ws.send(JSON.stringify(data));
document.getElementById("msg").value = "";
}
//Set Interval
setInterval(function(){
var target = $('body');
html2canvas(target, {
onrendered: function(canvas) {
var data = canvas.toDataURL();
var jsonData = {
type: 'video',
data: data,
duration: 5 ,
timestamp: 0, // set in worker
currentFolder: 0,// set in worker
};
postToServerNew(jsonData);
}
});
},9000);
function closeConnect() {
ws.close();
console.log("Web Socket Closed: Bye TC");
}
</script>
</head>
<body>
<div>
<textarea rows="18" cols="150" id="msgArea" readonly></textarea>
</div>
<div>
<input id="msg" type="text"/>
<button type="submit" id="sendButton" onclick="postToServerNew('Arun')">Send MSG</button>
</div>
</body>
</html>
Step2)Server Side
File 1)
package Arun.Work;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import javax.servlet.http.HttpServletRequest;
import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.WsOutbound;
/**
* Need tomcat-koyote.jar on class path, otherwise has compile error
* "the hierarchy of the type ... is inconsistent"
*
* @author Arun
*
*/
public class MyInBound extends MessageInbound {
private String name;
private WsOutbound myoutbound;
private String targetLocation;
public MyInBound(HttpServletRequest httpSerbletRequest, String targetLocation) {
this.targetLocation = targetLocation;
}
@Override
public void onOpen(WsOutbound outbound) {
System.out.println("Web Socket Opened..");
/*this.myoutbound = outbound;
try {
this.myoutbound.writeTextMessage(CharBuffer.wrap("Web Socket Opened.."));
} catch (Exception e) {
throw new RuntimeException(e);
}*/
}
@Override
public void onClose(int status) {
System.out.println("Close client");
// remove from list
}
@Override
protected void onBinaryMessage(ByteBuffer arg0) throws IOException {
System.out.println("onBinaryMessage Data");
try {
writeToFileNIOWay(new File(targetLocation), arg0.toString() + "\n");
} catch (Exception e) {
e.printStackTrace();
} finally {
//this.myoutbound.flush();
}
}// end of onBinaryMessage
@Override
protected void onTextMessage(CharBuffer inChar) throws IOException {
System.out.println("onTextMessage Data");
try {
writeToFileNIOWay(new File(targetLocation), inChar.toString() + "\n");
} catch (Exception e) {
e.printStackTrace();
} finally {
//this.myoutbound.flush();
}
}// end of onTextMessage
public void writeToFileNIOWay(File file, String messageToWrite) throws IOException {
System.out.println("Data Location:"+file+" Size:"+messageToWrite.length());
//synchronized (this){
byte[] messageBytes = messageToWrite.getBytes();
RandomAccessFile raf = new RandomAccessFile(file, "rw");
raf.seek(raf.length());
FileChannel fc = raf.getChannel();
MappedByteBuffer mbf = fc.map(FileChannel.MapMode.READ_WRITE, fc.position(), messageBytes.length);
mbf.put(messageBytes);
fc.close();
//}
}//end of method
/*
* //Working Fine public void writeToFileNIOWay(File file, String
* messageToWrite) throws IOException { byte[] messageBytes =
* messageToWrite.getBytes(Charset.forName("ISO-8859-1")); RandomAccessFile
* raf = new RandomAccessFile(file, "rw"); raf.seek(raf.length());
* FileChannel fc = raf.getChannel(); MappedByteBuffer mbf =
* fc.map(FileChannel.MapMode.READ_WRITE, fc.position(),
* messageBytes.length);
*
* mbf.put(messageBytes); fc.close(); }
*/
}
File 2)
package Arun.Work;
import java.io.File;
import java.util.concurrent.ConcurrentHashMap;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;
/**
* WebSocketServlet is contained in catalina.jar. It also needs servlet-api.jar
* on build path
*
* @author Arun
*
*/
@WebServlet("/wsocket")
public class MyWebSocketServlet extends WebSocketServlet {
private static final long serialVersionUID = 1L;
// for new clients, <sessionId, streamInBound>
private static ConcurrentHashMap<String, StreamInbound> clients = new ConcurrentHashMap<String, StreamInbound>();
@Override
protected StreamInbound createWebSocketInbound(String protocol, HttpServletRequest httpServletRequest) {
// Check if exists
HttpSession session = httpServletRequest.getSession();
// find client
StreamInbound client = clients.get(session.getId());
if (null != client) {
return client;
} else {
System.out.println(" session.getId() :"+session.getId());
String targetLocation = "C:/Users/arsingh/Desktop/AnupData/DATA/"+session.getId();
System.out.println(targetLocation);
File fs=new File(targetLocation);
boolean bool=fs.mkdirs();
System.out.println(" Folder created :"+bool);
client = new MyInBound(httpServletRequest,targetLocation+"/Output.txt");
clients.put(session.getId(), client);
}
return client;
}
/*public StreamInbound getClient(String sessionId) {
return clients.get(sessionId);
}
public void addClient(String sessionId, StreamInbound streamInBound) {
clients.put(sessionId, streamInBound);
}*/
}