扫描识别工具Dynamic Web TWAIN使用教程：属性/方法/事件介绍

属性

属性用于在运行时从Dynamic Web TWAIN中获取或设置特定的值，例如Resolution、Duplex、IfShowUI等。

/* Property *//* Scan pages in 200 DPI */DWObject.Resolution = 200;

方法

方法用于调用Dynamic Web TWAIN对象的内置函数，如AcquireImage、SaveAsJPEG、Rotate等。语法非常简单：

// Method ///<summary> /// Rotates the image of a specified index in buffer by a specified angle.  /// </summary>///<param name="sImageIndex" type="short">specifies the index of image in buffer. The index is 0-based.</param>///<param name="fAngle" type="float">specifies the angle.///<param name="bKeepSize" type="bool">specifies whether to keep the original size///<returns type="bool"></returns>DWObject.Rotate(0, 45, false); // rotate the 1st image in the buffer by 45 degrees

事件

当达到某个触发点时触发事件。例如，OnMouseClick鼠标点击事件等。与属性和方法相比，事件是有点难度的。在这里我们再多谈一下。 处理事件添加一个事件监听器 要添加事件监听器，可以使用内置方法RegisterEvent。请参考下面的示例代码：

<script type="text/javascript">Dynamsoft.WebTwainEnv.RegisterEvent('OnWebTwainReady', Dynamsoft_OnReady);var DWObject;/* OnWebTwainReady event fires as soon as Dynamic Web TWAIN is initialized and ready to be used. It is the best place to add event listeners */function Dynamsoft_OnReady() {   DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer');   DWObject.RegisterEvent("OnPostTransfer", Dynamsoft_OnPostTransfer);}function Dynamsoft_OnPostTransfer() {   /* This event OnPostTransfer will be triggered after a transfer ends. */   /* your code goes here*/}</script> 

 在上面的代码中，我们添加了JavaScript函数Dynamsoft_OnPostTransfer()作为事件OnPostTransfer的事件监听器。另外，你可以写这样的代码：

<script type="text/javascript">Dynamsoft.WebTwainEnv.RegisterEvent('OnWebTwainReady', Dynamsoft_OnReady);var DWObject;function Dynamsoft_OnReady() {   DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer');   DWObject.RegisterEvent("OnPostTransfer", function() {    /* your code goes here*/   });}</script>

 有参数的事件一些事件具有参数。以OnMouseClick事件为例：

/* sImageIndex is the index of the image you clicked on*/OnMouseClick(short sImageIndex) 

 当您创建相应的JavaScript函数（AKA，事件侦听器）时，可以包含参数并在运行时进行检索。

function DynamicWebTwain_OnMouseClick(index) {    CurrentImage.value = index + 1;}

或者

DWObject.RegisterEvent("OnPostTransfer", function(index) {    CurrentImage.value = index + 1;});

<script type="text/javascript">Dynamsoft.WebTwainEnv.RegisterEvent('OnWebTwainReady', Dynamsoft_OnReady);var DWObject;function Dynamsoft_OnReady() {   DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer');}</script>

或者

<script type="text/javascript">   Dynamsoft.WebTwainEnv.RegisterEvent('OnWebTwainReady', function() {     DWObject = Dynamsoft.WebTwainEnv.GetWebTwain('dwtcontrolContainer');   });</script>

本次教程到此结束，希望能对Dynamic Web TWAIN的用户带来帮助，接下来还会有更多的相关教程，敬请期待！

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标签：扫描识别扫描与图像