使用Dynamic Web TWAIN从网络摄像头捕获图像的综合指南
Dynamic Web TWAIN是一个专为Web应用程序设计的TWAIN扫描识别控件。你只需在TWAIN接口写几行代码，就可以用兼容TWAIN的扫描仪扫描文档或从数码相机/采集卡中获取图像。然后用户可以编辑图像并将图像保存为多种格式，用户可保存图像到远程数据库或者SharePoint。该TWAIN控件还支持上传和处理本地图像。
如何通过浏览器访问网络摄像头？
HTML5 为Web开发人员提供了JavaScript API MediaDevices.getUserMedia（）。在本指南中，我们将使用Dynamic Web TWAIN SDK网络摄像头插件构建一个在线网络摄像头演示。
为什么选择Dynamic Web TWAIN网络摄像头附加组件为什么有免费的选项时考虑付费选项？我们列出了HTML5不提供的网络摄像头附加组件的一些高级功能。
- 浏览器兼容性 – HTML5与某些较旧的浏览器不兼容，例如Internet Explorer 8。
- 精确控制网络摄像头 –您可以完全控制摄像机，例如摇摄，倾斜，滚动，变焦，曝光，光圈和自动对焦。
- 分辨率设置 –使用GetResolution（），SetResolution（）API获取和设置分辨率
- 扫描仪质量的图像 – Dynamsoft提供了多种图像增强技术来帮助用户生成高质量的图像，包括自动边界检测，噪声消除和透视校正。
- 上载到服务器 – SDK提供了内置方法，供用户将图像上载到服务器端。
如果您要构建一个健壮的，功能齐全的企业级应用程序，那么选择Dynamsoft的SDK这样的商业SDK将会为您带来巨大的投资回报。
关于Dynamic Web TWAIN网络摄像头附加组件
Dynamic Web TWAIN网络摄像头附加组件使Web开发人员可以使用JavaScript代码从网络摄像头捕获图像。网络摄像头SDK支持在Windows，macOS和Linux上的所有主流浏览器中嵌入视频流。Dynamic Web TWAIN还支持从移动相机捕获图像。设备支持
- 兼容UVC（USB视频类）的网络摄像头
- 内置笔记本电脑摄像头
- 文件相机
- Internet Explorer 8+
- 边缘
- 火狐浏览器
- 铬
服务器端支持
- Web服务器：Nginx，IIS，Tomcat，Apache等。
- 操作系统：Linux，Windows等。
- 语言：ASP.NET（C＃/ VB.NET），PHP，JSP等
如何逐步使用网络摄像头附加组件
在这里，我们将向您展示如何使用SDK轻松地将HTML网页中的网络摄像头捕获和视频预览集成。首先，下载Dynamic Web TWAIN并将Resources文件夹复制到您的项目中。然后创建一个新的网页HelloWorld.html。
步骤1添加参考
<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>
步骤＃2创建一个容器
<div id="dwtcontrolContainer"></div>
步骤＃3输入一个下拉列表和两个按钮
步骤＃4通过调用Dynamsoft_OnReady（）初始化对象
<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>
步骤＃5控制网络摄像头
您可以使用以下API播放和停止视频流：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);
}
}
步骤＃6通过使用CaptureImage（）捕获图像
function CaptureImage() {
if (DWObject) {
var funCaptureImage = function () {
SetIfWebcamPlayVideo(false);
};
DWObject.Addon.Webcam.CaptureImage(funCaptureImage, funCaptureImage);
}
}
如何同时从扫描仪和网络摄像头捕获图像
文档/记录管理应用程序通常需要通过Web浏览器从扫描仪和网络摄像机捕获图像。您可以使用Dynamic Web TWAIN核心SDK和网络摄像头附加组件轻松实现此目的。
让我们继续在HelloWorld.html网页上进行工作。
步骤＃1重写函数Dynamsoft_OnReady（）
要控制TWAIN扫描器，请调用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();
}
步骤＃2捕获图像
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); } } }
如何将扫描的图像上传到服务器端
步骤＃1添加用于上传的按钮步骤＃2上传图片
准备好图像后，您可以通过调用HTTPUploadThroughPost（）将其上传到Web服务器。
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);
}
}
该SDK支持ASP.NET（C＃/ VB.NET），PHP，JSP，ASP等，以在服务器端接收图像数据。PHP代码
<?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代码
<%@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＃）代码
<%@ 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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