Comment télécharger une capture d'écran en utilisant html2canvas?

Utilisation de html2canvas Comment puis-je enregistrer une capture d'écran sur un objet? J'ai exploré les démos et je vois que la fonction de générer la capture d'écran est générée comme suit:

$(window).ready(function() { ('body').html2canvas(); });

Ce que j'ai essayé de faire est

 $(window).ready(function() { canvasRecord = $('body').html2canvas(); dataURL = canvasRecord.toDataURL("image/png"); dataURL = dataURL.replace(/^data:image\/(png|jpg);base64,/, ""); upload(dataURL); });

Et, je le passe ensuite à ma fonction de upload() . Le problème que j'ai, c'est que je ne peux pas comprendre où la capture d'écran est faite dans la bibliothèque html2canvas() ou quelle fonction le renvoie. J'ai essayé de convertir l'objet canvas en utilisant cette réponse de SO (même si je ne suis pas certain que je dois faire cela).

Je viens de poser une question sur la façon de télécharger un fichier pour imgur , et les réponses là-bas (en particulier @ bebraw's) m'aident à comprendre ce que je dois faire.

La fonction upload() provient de l'exemple d'utilisation d'Imgur:

 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); }

J'ai modifié et annoté la méthode de cette réponse . Il envoie un seul fichier, avec un prénom, composé à partir d'un élément <canvas> .

 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')); }

Ce code fonctionne pour moi. Il générera une capture d'écran par html2canvas, télécharge la capture d'écran pour imgur api et renvoie l'URL imgur.

 <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>

 //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); }*/ }