浅谈OCR之Tesseract
光学字符识别(OCR,Optical Character Recognition)是指对文本资料进行扫描，而后对图像文件进行分析处理，获取文字及版面信息的过程。OCR技术很是专业，通常可能是印刷、打印行业的从业人员使用，能够快速的将纸质资料转换为电子资料。关于中文OCR，目前国内水平较高的有清华文通、汉王、尚书，其产品各有千秋，价格不菲。国外OCR发展较早，像一些大公司，如IBM、微软、HP等，即便没有推出单独的OCR产品，可是他们的研发团队早已掌握核心技术，将OCR功能植入了自身的软件系统。对于咱们程序员来讲，通常用不到那么高级的，主要在开发中可以集成基本的OCR功能就能够了。这两天我查找了不少免费OCR软件、类库，特意整理一下，今天首先来谈谈Tesseract，下一次将讨论下Onenote 2010中的OCR API实现。能够在这里查看OCR技术的发展简史。html
测试代码下载程序员
转载请注明出处：http://www.cnblogs.com/brooks-dotnet/archive/2010/10/05/1844203.html 小程序
一、Tesseract概述api
Tesseract的OCR引擎最早由HP实验室于1985年开始研发，至1995年时已经成为OCR业内最准确的三款识别引擎之一。然而，HP不久便决定放弃OCR业务，Tesseract也今后尘封。网络
数年之后，HP意识到，与其将Tesseract束之高阁，不如贡献给开源软件业，让其重焕新生－－2005年，Tesseract由美国内华达州信息技术研究所得到，并求诸于Google对Tesseract进行改进、消除Bug、优化工做。ide
Tesseract目前已做为开源项目发布在Google Project，其项目主页在这里查看，其最新版本3.0已经支持中文OCR，并提供了一个命令行工具。本次咱们来测试一下Tesseract 3.0，因为命令行对最终用户不太友好，我用WPF简单封装了一下，就能够方便的进行中文OCR了。工具
1.一、首先到Tesseract项目主页下载命令行工具、源代码、中文语言包：测试
1.二、命令行工具解压缩后以下（不含1.jpg、1.txt）：优化
1.三、为了进行中文OCR，将简体中文语言包复制到【tessdata】目录下：ui
1.四、在DOS下切换到Tesseract的命令行目录，查看一下tesseract.exe的命令格式：
Imagename为待OCR的图片，outputbase为OCR后的输出文件，默认是文本文件（.txt），lang为使用的语言包，configfile为配置文件。
1.五、下面来测试一下，准备一张jpg格式的图片，这里我是放到了和Tesseract同一个目录中：
输入：tesseract.exe 1.jpg 1 -l chi_sim，而后回车，几秒钟就OCR完成了：
这里注意命令的格式：imagename要加上扩展名.jpg，输出文件和语言包不须要加扩展名。
OCR结果：
能够看到结果不是很理想，中文识别还说的过去，可是英文、数字大都乱码。不过做为老牌的OCR引擎，能作到这种程度已经至关不错了，期待Google的后续升级吧，支持一下。
二、使用WPF封装Tesseract命令行
2.一、鉴于命令行书写容易出错，且对最终用户很不友好，我作了一个简单的WPF小程序，将Tesseract的命令行封装了一下：
左边选择图片、预览，右边选择输出目录，显示OCR结果，支持本地及网络图片的预览。
2.二、为了使得图片预览支持缩放、移动，本来打算使用微软的Zoom It API，惋惜不支持WPF，因而使用了一个第三方的类：
using System;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Animation;
using System.Windows;
using System.Windows.Media;
namespace PanAndZoom
{
public class PanAndZoomViewer : ContentControl
{
public double DefaultZoomFactor { get; set; }
private FrameworkElement source;
private Point ScreenStartPoint = new Point(0, 0);
private TranslateTransform translateTransform;
private ScaleTransform zoomTransform;
private TransformGroup transformGroup;
private Point startOffset;
public PanAndZoomViewer()
{
this.DefaultZoomFactor = 1.4;
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
Setup(this);
}
void Setup(FrameworkElement control)
{
this.source = VisualTreeHelper.GetChild(this, 0) as FrameworkElement;
this.translateTransform = new TranslateTransform();
this.zoomTransform = new ScaleTransform();
this.transformGroup = new TransformGroup();
this.transformGroup.Children.Add(this.zoomTransform);
this.transformGroup.Children.Add(this.translateTransform);
this.source.RenderTransform = this.transformGroup;
this.Focusable = true;
this.KeyDown += new KeyEventHandler(source_KeyDown);
this.MouseMove += new MouseEventHandler(control_MouseMove);
this.MouseDown += new MouseButtonEventHandler(source_MouseDown);
this.MouseUp += new MouseButtonEventHandler(source_MouseUp);
this.MouseWheel += new MouseWheelEventHandler(source_MouseWheel);
}
void source_KeyDown(object sender, KeyEventArgs e)
{
// hit escape to reset everything
if (e.Key == Key.Escape) Reset();
}
void source_MouseWheel(object sender, MouseWheelEventArgs e)
{
// zoom into the content. Calculate the zoom factor based on the direction of the mouse wheel.
double zoomFactor = this.DefaultZoomFactor;
if (e.Delta <= 0) zoomFactor = 1.0 / this.DefaultZoomFactor;
// DoZoom requires both the logical and physical location of the mouse pointer
var physicalPoint = e.GetPosition(this);
DoZoom(zoomFactor, this.transformGroup.Inverse.Transform(physicalPoint), physicalPoint);
}
void source_MouseUp(object sender, MouseButtonEventArgs e)
{
if (this.IsMouseCaptured)
{
// we're done. reset the cursor and release the mouse pointer
this.Cursor = Cursors.Arrow;
this.ReleaseMouseCapture();
}
}
void source_MouseDown(object sender, MouseButtonEventArgs e)
{
// Save starting point, used later when determining how much to scroll.
this.ScreenStartPoint = e.GetPosition(this);
this.startOffset = new Point(this.translateTransform.X, this.translateTransform.Y);
this.CaptureMouse();
this.Cursor = Cursors.ScrollAll;
}
void control_MouseMove(object sender, MouseEventArgs e)
{
if (this.IsMouseCaptured)
{
// if the mouse is captured then move the content by changing the translate transform.
// use the Pan Animation to animate to the new location based on the delta between the
// starting point of the mouse and the current point.
var physicalPoint = e.GetPosition(this);
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreatePanAnimation(physicalPoint.X - this.ScreenStartPoint.X + this.startOffset.X), HandoffBehavior.Compose);
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreatePanAnimation(physicalPoint.Y - this.ScreenStartPoint.Y + this.startOffset.Y), HandoffBehavior.Compose);
}
}
/// <summary>Helper to create the panning animation for x,y coordinates.</summary>
/// <param name="toValue">New value of the coordinate.</param>
/// <returns>Double animation</returns>
private DoubleAnimation CreatePanAnimation(double toValue)
{
var da = new DoubleAnimation(toValue, new Duration(TimeSpan.FromMilliseconds(300)));
da.AccelerationRatio = 0.1;
da.DecelerationRatio = 0.9;
da.FillBehavior = FillBehavior.HoldEnd;
da.Freeze();
return da;
}
/// <summary>Helper to create the zoom double animation for scaling.</summary>
/// <param name="toValue">Value to animate to.</param>
/// <returns>Double animation.</returns>
private DoubleAnimation CreateZoomAnimation(double toValue)
{
var da = new DoubleAnimation(toValue, new Duration(TimeSpan.FromMilliseconds(500)));
da.AccelerationRatio = 0.1;
da.DecelerationRatio = 0.9;
da.FillBehavior = FillBehavior.HoldEnd;
da.Freeze();
return da;
}
/// <summary>Zoom into or out of the content.</summary>
/// <param name="deltaZoom">Factor to mutliply the zoom level by. </param>
/// <param name="mousePosition">Logical mouse position relative to the original content.</param>
/// <param name="physicalPosition">Actual mouse position on the screen (relative to the parent window)</param>
public void DoZoom(double deltaZoom, Point mousePosition, Point physicalPosition)
{
double currentZoom = this.zoomTransform.ScaleX;
currentZoom *= deltaZoom;
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreateZoomAnimation(-1 * (mousePosition.X * currentZoom - physicalPosition.X)));
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreateZoomAnimation(-1 * (mousePosition.Y * currentZoom - physicalPosition.Y)));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleXProperty, CreateZoomAnimation(currentZoom));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleYProperty, CreateZoomAnimation(currentZoom));
}
/// <summary>Reset to default zoom level and centered content.</summary>
public void Reset()
{
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreateZoomAnimation(0));
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreateZoomAnimation(0));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleXProperty, CreateZoomAnimation(1));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleYProperty, CreateZoomAnimation(1));
}
}
}
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Animation;
using System.Windows;
using System.Windows.Media;
namespace PanAndZoom
{
public class PanAndZoomViewer : ContentControl
{
public double DefaultZoomFactor { get; set; }
private FrameworkElement source;
private Point ScreenStartPoint = new Point(0, 0);
private TranslateTransform translateTransform;
private ScaleTransform zoomTransform;
private TransformGroup transformGroup;
private Point startOffset;
public PanAndZoomViewer()
{
this.DefaultZoomFactor = 1.4;
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
Setup(this);
}
void Setup(FrameworkElement control)
{
this.source = VisualTreeHelper.GetChild(this, 0) as FrameworkElement;
this.translateTransform = new TranslateTransform();
this.zoomTransform = new ScaleTransform();
this.transformGroup = new TransformGroup();
this.transformGroup.Children.Add(this.zoomTransform);
this.transformGroup.Children.Add(this.translateTransform);
this.source.RenderTransform = this.transformGroup;
this.Focusable = true;
this.KeyDown += new KeyEventHandler(source_KeyDown);
this.MouseMove += new MouseEventHandler(control_MouseMove);
this.MouseDown += new MouseButtonEventHandler(source_MouseDown);
this.MouseUp += new MouseButtonEventHandler(source_MouseUp);
this.MouseWheel += new MouseWheelEventHandler(source_MouseWheel);
}
void source_KeyDown(object sender, KeyEventArgs e)
{
// hit escape to reset everything
if (e.Key == Key.Escape) Reset();
}
void source_MouseWheel(object sender, MouseWheelEventArgs e)
{
// zoom into the content. Calculate the zoom factor based on the direction of the mouse wheel.
double zoomFactor = this.DefaultZoomFactor;
if (e.Delta <= 0) zoomFactor = 1.0 / this.DefaultZoomFactor;
// DoZoom requires both the logical and physical location of the mouse pointer
var physicalPoint = e.GetPosition(this);
DoZoom(zoomFactor, this.transformGroup.Inverse.Transform(physicalPoint), physicalPoint);
}
void source_MouseUp(object sender, MouseButtonEventArgs e)
{
if (this.IsMouseCaptured)
{
// we're done. reset the cursor and release the mouse pointer
this.Cursor = Cursors.Arrow;
this.ReleaseMouseCapture();
}
}
void source_MouseDown(object sender, MouseButtonEventArgs e)
{
// Save starting point, used later when determining how much to scroll.
this.ScreenStartPoint = e.GetPosition(this);
this.startOffset = new Point(this.translateTransform.X, this.translateTransform.Y);
this.CaptureMouse();
this.Cursor = Cursors.ScrollAll;
}
void control_MouseMove(object sender, MouseEventArgs e)
{
if (this.IsMouseCaptured)
{
// if the mouse is captured then move the content by changing the translate transform.
// use the Pan Animation to animate to the new location based on the delta between the
// starting point of the mouse and the current point.
var physicalPoint = e.GetPosition(this);
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreatePanAnimation(physicalPoint.X - this.ScreenStartPoint.X + this.startOffset.X), HandoffBehavior.Compose);
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreatePanAnimation(physicalPoint.Y - this.ScreenStartPoint.Y + this.startOffset.Y), HandoffBehavior.Compose);
}
}
/// <summary>Helper to create the panning animation for x,y coordinates.</summary>
/// <param name="toValue">New value of the coordinate.</param>
/// <returns>Double animation</returns>
private DoubleAnimation CreatePanAnimation(double toValue)
{
var da = new DoubleAnimation(toValue, new Duration(TimeSpan.FromMilliseconds(300)));
da.AccelerationRatio = 0.1;
da.DecelerationRatio = 0.9;
da.FillBehavior = FillBehavior.HoldEnd;
da.Freeze();
return da;
}
/// <summary>Helper to create the zoom double animation for scaling.</summary>
/// <param name="toValue">Value to animate to.</param>
/// <returns>Double animation.</returns>
private DoubleAnimation CreateZoomAnimation(double toValue)
{
var da = new DoubleAnimation(toValue, new Duration(TimeSpan.FromMilliseconds(500)));
da.AccelerationRatio = 0.1;
da.DecelerationRatio = 0.9;
da.FillBehavior = FillBehavior.HoldEnd;
da.Freeze();
return da;
}
/// <summary>Zoom into or out of the content.</summary>
/// <param name="deltaZoom">Factor to mutliply the zoom level by. </param>
/// <param name="mousePosition">Logical mouse position relative to the original content.</param>
/// <param name="physicalPosition">Actual mouse position on the screen (relative to the parent window)</param>
public void DoZoom(double deltaZoom, Point mousePosition, Point physicalPosition)
{
double currentZoom = this.zoomTransform.ScaleX;
currentZoom *= deltaZoom;
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreateZoomAnimation(-1 * (mousePosition.X * currentZoom - physicalPosition.X)));
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreateZoomAnimation(-1 * (mousePosition.Y * currentZoom - physicalPosition.Y)));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleXProperty, CreateZoomAnimation(currentZoom));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleYProperty, CreateZoomAnimation(currentZoom));
}
/// <summary>Reset to default zoom level and centered content.</summary>
public void Reset()
{
this.translateTransform.BeginAnimation(TranslateTransform.XProperty, CreateZoomAnimation(0));
this.translateTransform.BeginAnimation(TranslateTransform.YProperty, CreateZoomAnimation(0));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleXProperty, CreateZoomAnimation(1));
this.zoomTransform.BeginAnimation(ScaleTransform.ScaleYProperty, CreateZoomAnimation(1));
}
}
}
2.三、除了使用鼠标。还能够使用滚动条调节图片预览效果：
<WrapPanel Grid.Row="2" Grid.Column="0">
<Label Name="lab长度" Content="长度：" Margin="3" />
<Slider Name="sl长度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="400" Value="{Binding ElementName=img图片, Path=Width, Mode=TwoWay}" />
<Label Name="lab宽度" Content="宽度：" Margin="3" />
<Slider Name="sl宽度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="400" Value="{Binding ElementName=img图片, Path=Height, Mode=TwoWay}" />
<Label Name="lab透明度" Content="透明度：" Margin="3" />
<Slider Name="sl透明度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="1" Value="{Binding ElementName=img图片, Path=Opacity, Mode=TwoWay}" />
<Label Name="lab拉伸方式" Content="拉伸方式：" Margin="3" />
<ComboBox Name="txt拉伸方式" Margin="3" MinWidth="85">
<ComboBoxItem Content="Fill" />
<ComboBoxItem Content="None" IsSelected="True" />
<ComboBoxItem Content="Uniform" />
<ComboBoxItem Content="UniformToFill" />
</ComboBox>
</WrapPanel>
<local:PanAndZoomViewer Grid.Row="3" Grid.Column="0" Height="300" Margin="3">
<Image Name="img图片" Stretch="{Binding ElementName=txt拉伸方式, Path=Text, Mode=TwoWay}" />
</local:PanAndZoomViewer>
<Label Name="lab长度" Content="长度：" Margin="3" />
<Slider Name="sl长度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="400" Value="{Binding ElementName=img图片, Path=Width, Mode=TwoWay}" />
<Label Name="lab宽度" Content="宽度：" Margin="3" />
<Slider Name="sl宽度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="400" Value="{Binding ElementName=img图片, Path=Height, Mode=TwoWay}" />
<Label Name="lab透明度" Content="透明度：" Margin="3" />
<Slider Name="sl透明度" MinWidth="50" Margin="3" VerticalAlignment="Center" Maximum="1" Value="{Binding ElementName=img图片, Path=Opacity, Mode=TwoWay}" />
<Label Name="lab拉伸方式" Content="拉伸方式：" Margin="3" />
<ComboBox Name="txt拉伸方式" Margin="3" MinWidth="85">
<ComboBoxItem Content="Fill" />
<ComboBoxItem Content="None" IsSelected="True" />
<ComboBoxItem Content="Uniform" />
<ComboBoxItem Content="UniformToFill" />
</ComboBox>
</WrapPanel>
<local:PanAndZoomViewer Grid.Row="3" Grid.Column="0" Height="300" Margin="3">
<Image Name="img图片" Stretch="{Binding ElementName=txt拉伸方式, Path=Text, Mode=TwoWay}" />
</local:PanAndZoomViewer>
2.四、因为Tesseract命令行不支持直接OCR网络图片，故先下载：
private void fnStartDownload(string v_strImgPath, string v_strOutputDir, out string v_strTmpPath)
{
int n = v_strImgPath.LastIndexOf('/');
string URLAddress = v_strImgPath.Substring(0, n);
string fileName = v_strImgPath.Substring(n + 1, v_strImgPath.Length - n - 1);
this.__OutputFileName = v_strOutputDir + "\\" + fileName.Substring(0, fileName.LastIndexOf("."));
if (!Directory.Exists(System.Configuration.ConfigurationManager.AppSettings["tmpPath"]))
{
Directory.CreateDirectory(System.Configuration.ConfigurationManager.AppSettings["tmpPath"]);
}
string Dir = System.Configuration.ConfigurationManager.AppSettings["tmpPath"];
v_strTmpPath = Dir + "\\" + fileName;
WebRequest myre = WebRequest.Create(URLAddress);
client.DownloadFile(v_strImgPath, v_strTmpPath);
//Stream str = client.OpenRead(v_strImgPath);
//StreamReader reader = new StreamReader(str);
//byte[] mbyte = new byte[Int32.Parse(System.Configuration.ConfigurationManager.AppSettings["MaxDownloadImgLength"])];
//int allmybyte = (int)mbyte.Length;
//int startmbyte = 0;
//while (allmybyte > 0)
//{
// int m = str.Read(mbyte, startmbyte, allmybyte);
// if (m == 0)
// {
// break;
// }
// startmbyte += m;
// allmybyte -= m;
//}
//FileStream fstr = new FileStream(v_strTmpPath, FileMode.Create, FileAccess.Write);
//fstr.Write(mbyte, 0, startmbyte);
//str.Close();
//fstr.Close();
}
{
int n = v_strImgPath.LastIndexOf('/');
string URLAddress = v_strImgPath.Substring(0, n);
string fileName = v_strImgPath.Substring(n + 1, v_strImgPath.Length - n - 1);
this.__OutputFileName = v_strOutputDir + "\\" + fileName.Substring(0, fileName.LastIndexOf("."));
if (!Directory.Exists(System.Configuration.ConfigurationManager.AppSettings["tmpPath"]))
{
Directory.CreateDirectory(System.Configuration.ConfigurationManager.AppSettings["tmpPath"]);
}
string Dir = System.Configuration.ConfigurationManager.AppSettings["tmpPath"];
v_strTmpPath = Dir + "\\" + fileName;
WebRequest myre = WebRequest.Create(URLAddress);
client.DownloadFile(v_strImgPath, v_strTmpPath);
//Stream str = client.OpenRead(v_strImgPath);
//StreamReader reader = new StreamReader(str);
//byte[] mbyte = new byte[Int32.Parse(System.Configuration.ConfigurationManager.AppSettings["MaxDownloadImgLength"])];
//int allmybyte = (int)mbyte.Length;
//int startmbyte = 0;
//while (allmybyte > 0)
//{
// int m = str.Read(mbyte, startmbyte, allmybyte);
// if (m == 0)
// {
// break;
// }
// startmbyte += m;
// allmybyte -= m;
//}
//FileStream fstr = new FileStream(v_strTmpPath, FileMode.Create, FileAccess.Write);
//fstr.Write(mbyte, 0, startmbyte);
//str.Close();
//fstr.Close();
}
2.五、使用Process来调用Tesseract命令行：
private void fnOCR(string v_strTesseractPath, string v_strSourceImgPath, string v_strOutputPath, string v_strLangPath)
{
using (Process process = new System.Diagnostics.Process())
{
process.StartInfo.FileName = v_strTesseractPath;
process.StartInfo.Arguments = v_strSourceImgPath + " " + v_strOutputPath + " -l " + v_strLangPath;
process.StartInfo.UseShellExecute = false;
process.StartInfo.CreateNoWindow = true;
process.StartInfo.RedirectStandardOutput = true;
process.Start();
process.WaitForExit();
}
}
{
using (Process process = new System.Diagnostics.Process())
{
process.StartInfo.FileName = v_strTesseractPath;
process.StartInfo.Arguments = v_strSourceImgPath + " " + v_strOutputPath + " -l " + v_strLangPath;
process.StartInfo.UseShellExecute = false;
process.StartInfo.CreateNoWindow = true;
process.StartInfo.RedirectStandardOutput = true;
process.Start();
process.WaitForExit();
}
}
2.六、测试本地图片：
2.七、测试网络图片：
小结：
本次咱们简单讨论了下Tesseract的用法，做为一款开源、免费的OCR引擎，可以支持中文十分可贵。虽然其识别效果不是很理想，可是对于要求不高的中小型项目来讲，已经足够用了。这里有一份免费OCR工具列表，感兴趣的朋友能够研究一下。下一次将测试一下Onenote 2010中OCR功能，以及如何调用其API，为项目所用。