OCR

OCR（optical character recognition），光学字符识别。

      OCR文字识别是指电子设备（例如扫描仪或数码相机）检查纸上打印的字符，然后用字符识别方法将形状翻译成计算机文字的过程；即，对文本资料进行扫描，然后对图像文件进行分析处理，获取文字及版面信息的过程。
      如何除错或利用辅助信息提高识别正确率，是OCR最重要的课题。
      衡量一个OCR系统性能好坏的主要指标有：拒识率、误识率、识别速度、用户界面的友好性，产品的稳定性，易用性及可行性等。
      OCR技术的实现，总体上可以分为五步：预处理图片、切割字符、识别字符、恢复版面、后处理文字。中间的三步是核心，头尾两步最难。

C#中使用Spire.OCR框架可以识别图片中的字母、文字、数字等。

一、Demo测试

VS2019中新建窗体应用程序ImageRecognitionTextDemo，将默认的Form1重命名为FormImageRecognitionText。

右键项目属性

选择目标平台为X64 

右键项目 ImageRecognitionTextDemo，选择【管理NuGet程序包】 ，搜索Spire.OCR

安装Nuget包完成

将下载如下非托管dll放在应用程序的debug下，或者 复制到项目根目录下，选择始终复制。

 注意托管Spire.OCR.dll需要自动引用如上六个框架包，因此Spire.OCR.dll和六个框架包必须在同一路径下。

二、窗体FormImageRecognitionText设计器代码如下

文件 FormImageRecognitionText.Designer.cs源程序如下：

namespace ImageRecognitionTextDemo
{
    partial class FormImageRecognitionText
    {
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// 清理所有正在使用的资源。
        /// </summary>
        /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗体设计器生成的代码

        /// <summary>
        /// 设计器支持所需的方法 - 不要修改
        /// 使用代码编辑器修改此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            this.pictureBox1 = new System.Windows.Forms.PictureBox();
            this.rtxbDisplay = new System.Windows.Forms.RichTextBox();
            this.btnOpen = new System.Windows.Forms.Button();
            this.btnRecognize = new System.Windows.Forms.Button();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
            this.SuspendLayout();
            // 
            // pictureBox1
            // 
            this.pictureBox1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
            this.pictureBox1.Location = new System.Drawing.Point(12, 12);
            this.pictureBox1.Name = "pictureBox1";
            this.pictureBox1.Size = new System.Drawing.Size(400, 400);
            this.pictureBox1.TabIndex = 0;
            this.pictureBox1.TabStop = false;
            // 
            // rtxbDisplay
            // 
            this.rtxbDisplay.Location = new System.Drawing.Point(418, 12);
            this.rtxbDisplay.Name = "rtxbDisplay";
            this.rtxbDisplay.ReadOnly = true;
            this.rtxbDisplay.Size = new System.Drawing.Size(562, 715);
            this.rtxbDisplay.TabIndex = 1;
            this.rtxbDisplay.Text = "";
            // 
            // btnOpen
            // 
            this.btnOpen.Font = new System.Drawing.Font("宋体", 13F, System.Drawing.FontStyle.Bold);
            this.btnOpen.Location = new System.Drawing.Point(51, 439);
            this.btnOpen.Name = "btnOpen";
            this.btnOpen.Size = new System.Drawing.Size(104, 56);
            this.btnOpen.TabIndex = 2;
            this.btnOpen.Text = "打开图片";
            this.btnOpen.UseVisualStyleBackColor = true;
            this.btnOpen.Click += new System.EventHandler(this.btnOpen_Click);
            // 
            // btnRecognize
            // 
            this.btnRecognize.Font = new System.Drawing.Font("宋体", 13F, System.Drawing.FontStyle.Bold);
            this.btnRecognize.Location = new System.Drawing.Point(217, 439);
            this.btnRecognize.Name = "btnRecognize";
            this.btnRecognize.Size = new System.Drawing.Size(104, 56);
            this.btnRecognize.TabIndex = 3;
            this.btnRecognize.Text = "识别图片";
            this.btnRecognize.UseVisualStyleBackColor = true;
            this.btnRecognize.Click += new System.EventHandler(this.btnRecognize_Click);
            // 
            // FormImageRecognitionText
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(982, 739);
            this.Controls.Add(this.btnRecognize);
            this.Controls.Add(this.btnOpen);
            this.Controls.Add(this.rtxbDisplay);
            this.Controls.Add(this.pictureBox1);
            this.Name = "FormImageRecognitionText";
            this.Text = "图像识别文本框架OCR";
            this.Load += new System.EventHandler(this.FormImageRecognitionText_Load);
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.PictureBox pictureBox1;
        private System.Windows.Forms.RichTextBox rtxbDisplay;
        private System.Windows.Forms.Button btnOpen;
        private System.Windows.Forms.Button btnRecognize;
    }
}

三、FormImageRecognitionText窗体源程序如下：

程序文件FormImageRecognitionText.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Spire.OCR;

namespace ImageRecognitionTextDemo
{
    public partial class FormImageRecognitionText : Form
    {
        public FormImageRecognitionText()
        {
            InitializeComponent();
        }

        private void FormImageRecognitionText_Load(object sender, EventArgs e)
        {
            //C# .NET实现扫描识别图片中的文字 Spire.OCR
            //OCR:光学字符识别。
            /*
             * OCR（optical character recognition）文字识别是指电子设备（例如扫描仪或数码相机）检查纸上打印的字符，
             * 然后用字符识别方法将形状翻译成计算机文字的过程；即，对文本资料进行扫描，然后对图像文件进行分析处理，获取文字及版面信息的过程。
             * 如何除错或利用辅助信息提高识别正确率，是OCR最重要的课题。
             * 衡量一个OCR系统性能好坏的主要指标有：拒识率、误识率、识别速度、用户界面的友好性，产品的稳定性，易用性及可行性等。
             * OCR技术的实现，总体上可以分为五步：预处理图片、切割字符、识别字符、恢复版面、后处理文字。中间的三步是核心，头尾两步最难。
             * 百家号技术：
             * https://baijiahao.baidu.com/s?id=1744946979174786023&wfr=spider&for=pc
            */
            pictureBox1.BackgroundImageLayout = ImageLayout.Zoom;
        }

        /// <summary>
        /// 显示文本框内容
        /// </summary>
        /// <param name="message"></param>
        private void DisplayContent(string message)
        {
            this.BeginInvoke(new Action(() =>
            {
                if (rtxbDisplay.TextLength > 10240)
                {
                    rtxbDisplay.Clear();
                }
                rtxbDisplay.AppendText($"{DateTime.Now.ToString("HH:mm:ss.fff")}->{message}\n");
                rtxbDisplay.ScrollToCaret();
            }));
            Application.DoEvents();
        }

        /// <summary>
        /// 显示OCR处理结果
        /// </summary>
        /// <param name="ocrScanner"></param>
        /// <param name="stopwatch"></param>
        /// <param name="result"></param>
        private void DisplayProcessResultOCR(OcrScanner ocrScanner, System.Diagnostics.Stopwatch stopwatch, bool result)
        {
            IOCRText text = ocrScanner.Text;
            IOCRTextBlock[] ocrTextBlocks = text.Blocks;
            stopwatch.Stop();
            DisplayContent($"识别图片完成,耗时【{stopwatch.Elapsed.TotalMilliseconds}】ms：识别结果【{result}】,文本块个数【{ocrTextBlocks.Length}】");
            for (int i = 0; i < ocrTextBlocks.Length; i++)
            {
                DisplayContent($"第【{(i + 1).ToString("D2")}】个文本块:");
                DisplayContent($"  Text:【{ocrTextBlocks[i].Text}】");
                DisplayContent($"  Confidence:【{ocrTextBlocks[i].Confidence}】");
                DisplayContent($"  Level:【{ocrTextBlocks[i].Level}】");
                DisplayContent($"  IsTruncated:【{ocrTextBlocks[i].IsTruncated}】");
                DisplayContent($"  Box:【{ocrTextBlocks[i].Box}】");
                //DisplayContent($"  TextBlock:【{ocrTextBlocks[i].TextBlock == null}】");
            }
            MessageBox.Show(text.ToString());
        }

        private async void btnOpen_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = "jpeg|*.jpg|bmp|*.bmp|gif|*.gif|png|*.png|tiff|*.tiff|All|*.*";
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                string fileName = openFileDialog.FileName;
                pictureBox1.BackgroundImage = Image.FromFile(fileName);

                await Task.Run(new Action(() =>
                {
                    OcrScanner ocrScanner = new OcrScanner();
                    System.Diagnostics.Stopwatch stopwatch = System.Diagnostics.Stopwatch.StartNew();
                    DisplayContent($"开始识别图片：【{fileName}】");
                    bool result = ocrScanner.Scan(fileName);
                    DisplayProcessResultOCR(ocrScanner, stopwatch, result);
                }));
            }
        }

        private async void btnRecognize_Click(object sender, EventArgs e)
        {
            MemoryStream memoryStream = new MemoryStream();
            pictureBox1.BackgroundImage.Save(memoryStream, pictureBox1.BackgroundImage.RawFormat);
            await Task.Run(new Action(() =>
            {
                OcrScanner ocrScanner = new OcrScanner();
                System.Diagnostics.Stopwatch stopwatch = System.Diagnostics.Stopwatch.StartNew();
                DisplayContent($"开始识别图片：图片大小【{memoryStream.Length / 1024}】KB");
                OCRImageFormat imageFormat;
                Enum.TryParse(pictureBox1.BackgroundImage.RawFormat.ToString(), true, out imageFormat);
                bool result = ocrScanner.Scan(memoryStream, imageFormat);
                DisplayProcessResultOCR(ocrScanner, stopwatch, result);
            }));
        }
    }
}

四、测试运行如下：