使用Dynamic Web TWAIN從網絡攝像頭捕獲圖像的綜合指南
Dynamic Web TWAIN是一個專為Web應用程序設計的TWAIN掃描識別控件。你只需在TWAIN接口寫幾行代碼，就可以用兼容TWAIN的掃描儀掃描文檔或從數碼相機/采集卡中獲取圖像。然后用戶可以編輯圖像并將圖像保存為多種格式，用戶可保存圖像到遠程數據庫或者SharePoint。該TWAIN控件還支持上傳和處理本地圖像。
如何通過瀏覽器訪問網絡攝像頭？
HTML5 為Web開發人員提供了JavaScript API MediaDevices.getUserMedia（）。在本指南中，我們將使用Dynamic Web TWAIN SDK網絡攝像頭插件構建一個在線網絡攝像頭演示。
為什么選擇Dynamic Web TWAIN網絡攝像頭附加組件為什么有免費的選項時考慮付費選項？我們列出了HTML5不提供的網絡攝像頭附加組件的一些高級功能。
- 瀏覽器兼容性 – HTML5與某些較舊的瀏覽器不兼容，例如Internet Explorer 8。
- 精確控制網絡攝像頭 –您可以完全控制攝像機，例如搖攝，傾斜，滾動，變焦，曝光，光圈和自動對焦。
- 分辨率設置 –使用GetResolution（），SetResolution（）API獲取和設置分辨率
- 掃描儀質量的圖像 – Dynamsoft提供了多種圖像增強技術來幫助用戶生成高質量的圖像，包括自動邊界檢測，噪聲消除和透視校正。
- 上載到服務器 – SDK提供了內置方法，供用戶將圖像上載到服務器端。
如果您要構建一個健壯的，功能齊全的企業級應用程序，那么選擇Dynamsoft的SDK這樣的商業SDK將會為您帶來巨大的投資回報。
關于Dynamic Web TWAIN網絡攝像頭附加組件
Dynamic Web TWAIN網絡攝像頭附加組件使Web開發人員可以使用JavaScript代碼從網絡攝像頭捕獲圖像。網絡攝像頭SDK支持在Windows，macOS和Linux上的所有主流瀏覽器中嵌入視頻流。Dynamic Web TWAIN還支持從移動相機捕獲圖像。設備支持
- 兼容UVC（USB視頻類）的網絡攝像頭
- 內置筆記本電腦攝像頭
- 文件相機
- Internet Explorer 8+
- 邊緣
- 火狐瀏覽器
- 鉻
服務器端支持
- Web服務器：Nginx，IIS，Tomcat，Apache等。
- 操作系統：Linux，Windows等。
- 語言：ASP.NET（C＃/ VB.NET），PHP，JSP等
如何逐步使用網絡攝像頭附加組件
在這里，我們將向您展示如何使用SDK輕松地將HTML網頁中的網絡攝像頭捕獲和視頻預覽集成。首先，下載Dynamic Web TWAIN并將Resources文件夾復制到您的項目中。然后創建一個新的網頁HelloWorld.html。
步驟1添加參考
<head>
<script src="Resources/dynamsoft.webtwain.initiate.js"> </script>
<script src="Resources/dynamsoft.webtwain.config.js"> </script>
<script src="Resources/addon/dynamsoft.webtwain.addon.webcam.js"> </script>
</head>
步驟＃2創建一個容器
<div id="dwtcontrolContainer"></div>
步驟＃3輸入一個下拉列表和兩個按鈕
步驟＃4通過調用Dynamsoft_OnReady（）初始化對象
<script type="text/javascript">
var DWObject;
var isVideoOn = true;
function Dynamsoft_OnReady() {
DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer'); // Get the Dynamic Web TWAIN object that is embedded in the div with id 'dwtcontrolContainer'
if (DWObject) {
DWObject.Width = 504;
DWObject.Height = 600;
var arySource = DWObject.Addon.Webcam.GetSourceList();
for (var i = 0; i < arySource.length; i++)
document.getElementById("source").options.add(new Option(arySource[i], arySource[i]), i); // Get Webcam Source names and put them in a drop-down box
}
document.getElementById('source').onchange = function () {
DWObject.Addon.Webcam.SelectSource(document.getElementById("source").options[document.getElementById("source").selectedIndex].value);
SetIfWebcamPlayVideo(true);
}
document.getElementById('source').onchange();
}
</script>
步驟＃5控制網絡攝像頭
您可以使用以下API播放和停止視頻流：DWObject.Addon.Webcam.StopVideo（）和DWObject.Addon.Webcam.PlayVideo（DWObject，80,function（）{}）。
function enableButton(element) {
element.style.backgroundColor = "";
element.disabled = "";
}
function disableButton(element) {
element.style.backgroundColor = "#aaa";
element.disabled = "disabled";
}
function SetIfWebcamPlayVideo(bShow) {
if (bShow) {
DWObject.Addon.Webcam.StopVideo();
DWObject.Addon.Webcam.PlayVideo(DWObject, 80, function () { });
isVideoOn = true;
enableButton(document.getElementById("btn-grab"));
document.getElementById("btn-switch").value = "Hide Video";
}
else {
DWObject.Addon.Webcam.StopVideo();
isVideoOn = false;
disableButton(document.getElementById("btn-grab"));
document.getElementById("btn-switch").value = "Show Video";
}
}
function SwitchViews() {
if (isVideoOn == false) {
// continue the video
SetIfWebcamPlayVideo(true);
} else {
// stop the video
SetIfWebcamPlayVideo(false);
}
}
步驟＃6通過使用CaptureImage（）捕獲圖像
function CaptureImage() {
if (DWObject) {
var funCaptureImage = function () {
SetIfWebcamPlayVideo(false);
};
DWObject.Addon.Webcam.CaptureImage(funCaptureImage, funCaptureImage);
}
}
如何同時從掃描儀和網絡攝像頭捕獲圖像
文檔/記錄管理應用程序通常需要通過Web瀏覽器從掃描儀和網絡攝像機捕獲圖像。您可以使用Dynamic Web TWAIN核心SDK和網絡攝像頭附加組件輕松實現此目的。
讓我們繼續在HelloWorld.html網頁上進行工作。
步驟＃1重寫函數Dynamsoft_OnReady（）
要控制TWAIN掃描器，請調用API：DWObject = Dynamsoft.WebTwainEnv.GetWebTwain（'dwtcontrolContainer'） Dynamsoft.WebTwainEnv.AutoLoad = false;
Dynamsoft.WebTwainEnv.RegisterEvent('OnWebTwainReady', Dynamsoft_OnReady); // Register OnWebTwainReady event. This event fires as soon as Dynamic Web TWAIN is initialized and ready to be used
var webCamStartingIndex;//This is used to separate scanners and webcams
var DWObject;
var isVideoOn = true;
function Dynamsoft_OnReady() {
DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer'); // Get the Dynamic Web TWAIN object that is embedded in the div with id 'dwtcontrolContainer'
if (DWObject) {
DWObject.Width = 504;
DWObject.Height = 600;
document.getElementById('source').options.length = 0;
var count = DWObject.SourceCount;
for (var i = 0; i < count; i++) { document.getElementById('source').options.add(new Option(DWObject.GetSourceNameItems(i), i)); } webCamStartingIndex = i; var arySource = DWObject.Addon.Webcam.GetSourceList(); for (var i = 0; i < arySource.length; i++) document.getElementById("source").options.add(new Option(arySource[i], arySource[i]), i + webCamStartingIndex); // Get Webcam Source names and put them in a drop-down box } document.getElementById('source').onchange = function () { if (document.getElementById('source').selectedIndex < webCamStartingIndex) { if (arySource.length > 0)
DWObject.Addon.Webcam.StopVideo();
isVideoOn = false;
document.getElementById("btn-grab").style.backgroundColor = "";
document.getElementById('btn-grab').value = 'Acquire From a Scanner';
document.getElementById("btn-switch").style.display = 'none';
}
else {
DWObject.Addon.Webcam.SelectSource(document.getElementById("source").options[document.getElementById("source").selectedIndex].value);
SetIfWebcamPlayVideo(true);
document.getElementById('btn-grab').value = 'Acquire From a Webcam';
document.getElementById("btn-switch").style.display = '';
}
document.getElementById("btn-grab").disabled = "";
}
document.getElementById('source').onchange();
}
步驟＃2捕獲圖像
function CaptureImage() {
if (DWObject) {
if (document.getElementById('source').selectedIndex < webCamStartingIndex) { DWObject.IfShowUI = true; DWObject.IfDisableSourceAfterAcquire = true; DWObject.SelectSourceByIndex(document.getElementById('source').selectedIndex); DWObject.CloseSource(); DWObject.OpenSource(); DWObject.AcquireImage(); } else { var funCaptureImage = function () { SetIfWebcamPlayVideo(false); }; DWObject.Addon.Webcam.CaptureImage(funCaptureImage, funCaptureImage); } } }
如何將掃描的圖像上傳到服務器端
步驟＃1添加用于上傳的按鈕步驟＃2上傳圖片
準備好圖像后，您可以通過調用HTTPUploadThroughPost（）將其上傳到Web服務器。
function upload() {
if (DWObject) {
// If no image in buffer, return the function
if (DWObject.HowManyImagesInBuffer == 0)
return;
var strHTTPServer = location.hostname; //The name of the HTTP server. For example: "www.dynamsoft.com";
var CurrentPathName = unescape(location.pathname);
var CurrentPath = CurrentPathName.substring(0, CurrentPathName.lastIndexOf("/") + 1);
var strActionPage = CurrentPath + "filename"; // Action page
DWObject.IfSSL = false; // Set whether SSL is used
DWObject.HTTPPort = location.port == "" ? 80 : location.port;
var Digital = new Date();
var uploadfilename = Digital.getMilliseconds(); // Uses milliseconds according to local time as the file name
//Upload image in JPEG
DWObject.HTTPUploadThroughPost(strHTTPServer, DWObject.CurrentImageIndexInBuffer, strActionPage, uploadfilename + ".jpg", OnHttpUploadSuccess, OnHttpUploadFailure);
}
}
該SDK支持ASP.NET（C＃/ VB.NET），PHP，JSP，ASP等，以在服務器端接收圖像數據。PHP代碼
<?php
$strJson = "{\"success\":false}";
try{
$file = $_FILES["RemoteFile"];
$fileName = $_POST["fileName"];
if ($fileName == "" || $fileName == null) $fileName = $file["name"];
$filePath = dirname(__FILE__) . "/upload/";
if (!file_exists($filePath)) {
mkdir($filePath);
}
if (file_exists($filePath . $fileName))
{
$iniNum = 0;
if (strpos($fileName, "(") !== FALSE && strpos($fileName, ")") !== FALSE)
{
$leftPhPos = strrpos($fileName, "(");
$rightPhPos = strrpos($fileName, ")");
if ($leftPhPos < $rightPhPos) {
$numStr = substr($fileName, $leftPhPos + 1, $rightPhPos - $leftPhPos - 1);
if (is_numeric($numStr))
{
$iniNum = intval($numStr);
$fileName = substr($fileName, 0, $leftPhPos) . substr($fileName, $rightPhPos + 1);
}
else {
$iniNum = 0;
}
}
}
$indexPoint = strrpos($fileName, ".");
$str1 = substr($fileName, 0, $indexPoint) . "(";
$str2 = ")" . substr($fileName, $indexPoint);
for ($i = $iniNum; ; ++$i)
{
if (!file_exists($filePath . ($str1 . $i . $str2)))
{
$fileName = $str1 . $i . $str2;
break;
}
}
}
$fileFullPath = $filePath . $fileName;
if(strpos($file["type"], 'text/plain') === false){
move_uploaded_file($file["tmp_name"] , $fileFullPath);
}else{
$file_contents = base64_decode(str_replace(' ', '+', file_get_contents($file['tmp_name'])));
file_put_contents($fileFullPath, $file_contents);
}
$strJson = "{\"success\":true, \"fileName\":\"" . $fileName . "\"}";
}
catch(Exception $ex){
$strJson = "{\"success\":false, \"error\": \"" . ex.Message.Replace("\\", "\\\\") . "\"}";
}
// Response.Clear();
header("Content-Type: application/json; charset=utf-8");
echo $strJson;
?>
JSP代碼
<%@page import="java.util.*,java.io.File,java.io.FileOutputStream,org.apache.commons.fileupload.FileUpload,org.apache.commons.fileupload.FileItem,org.apache.commons.fileupload.disk.DiskFileItemFactory,org.apache.commons.fileupload.servlet.ServletFileUpload,sun.misc.BASE64Decoder"%>
<%@page contentType="application/json; charset=utf-8" %>
<%@page language="java" %>
<% String strJson = "{\"success\":false}"; try{ // get more info from: //commons.apache.org/proper/commons-fileupload/ DiskFileItemFactory factory = new DiskFileItemFactory(); ServletContext servletContext = this.getServletConfig().getServletContext(); File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir"); factory.setRepository(repository); ServletFileUpload upload = new ServletFileUpload(factory); List items = upload.parseRequest(request);
Iterator iter = items.iterator();
String fileName = null;
String tempFileName = null;
String contentType = null;
FileItem fileItem = null;
while (iter.hasNext()) {
FileItem item = iter.next();
String fieldName = item.getFieldName();
if(fieldName.equals("fileName")){
fileName = item.getString();
}else if(fieldName.equals("RemoteFile")){
tempFileName = item.getName();
contentType = item.getContentType();
fileItem = item;
}
}
if(fileName == null || fileName.isEmpty()){
fileName = tempFileName;
}
String path = application.getRealPath(request.getServletPath());
String dir = new java.io.File(path).getParent();
String filePath = dir + "/UploadedImages/" + fileName;
File file = new File(filePath);
if(!file.getParentFile().exists()){
file.getParentFile().mkdir();
}
if(!file.exists()){
file.createNewFile();
}
if(!contentType.contains("text/plain")){
fileItem.write(file);
}else{
String base64Str = fileItem.getString();
byte[] b = null;
b = (new BASE64Decoder()).decodeBuffer(base64Str);
FileOutputStream fileOutStream = new FileOutputStream(file);
fileOutStream.write(b);
fileOutStream.flush();
fileOutStream.close();
}
strJson = "{\"success\":true, \"fileName\":\"" + fileName + "\"}";
}
catch(Exception ex){
strJson = "{\"success\":false, \"error\": \"" + ex.getMessage().replace("\\", "\\\\") + "\"}";
}
out.clear();
out.write(strJson);
out.close();
%>
ASP.NET（C＃）代碼
<%@ Page Language="C#" %>
<%@ Import Namespace="System.IO" %>
<% string strJson = "{\"success\":false}"; try { HttpPostedFile file = Request.Files["RemoteFile"]; string fileName = Request.Form["fileName"]; if (string.IsNullOrEmpty(fileName)) fileName = file.FileName; string filePath = Server.MapPath(".") + "\\UploadedImages\\" + fileName; if (!file.ContentType.Contains("text/plain")) { file.SaveAs(filePath); } else { Stream fs = file.InputStream; byte[] base64Bytes = new byte[fs.Length]; fs.Read(base64Bytes, 0, (int) fs.Length); StringBuilder base64Str = new StringBuilder(); foreach (byte b in base64Bytes) { base64Str.Append((char) b); } File.WriteAllBytes(filePath, Convert.FromBase64String(base64Str.ToString())); } strJson = "{\"success\":true, \"fileName\":\"" + fileName + "\"}"; } catch (Exception ex) { strJson = "{\"success\":false, \"error\": \"" + ex.Message.Replace("\\", "\\\\") + "\"}"; } Response.Clear(); Response.ContentType = "application/json; charset=utf-8"; Response.Write(strJson); Response.End(); %>
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