最近做笔记需要一个截图后获取图中文字的轻型程序，最好直接按快捷键就能识别并将文字自动复制。网上的应该都是要钱的，或者东西太杂了看着乱得慌，于是决定自己写。我c#只稍微学了一点，讲的不好的地方代码不规范的地方见谅。

我使用的是百度的文字识别api，请先自己去申请一下资源，免费的，一个月免费识别1000次好像是。然后截图直接用的Snipaste这个软件，贼好用。

api主页：https://ai.baidu.com/tech/ocr/general

然后领取免费资源，创建应用使用。

一、创建项目

创建一个窗口应用项目

然后右键引用 - 管理NuGet程序包，安装Newtonsoft.Json和System.Net.Http

二、编写基本识别代码

首先去百度api的控制台获取一下api key和secret key，网址：百度智能云-登录

然后进入文档，里面请求的基本代码已经给我们写好了，直接复制就ok了，文字识别我们用高精度版的。

获取AccessToken文档：https://ai.baidu.com/ai-doc/REFERENCE/Ck3dwjhhu

文字识别文档：https://ai.baidu.com/ai-doc/OCR/1k3h7y3db

MainForm.cs

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Windows.Forms;
using Newtonsoft.Json;
using System.Text.RegularExpressions;
using System.IO;
using System.Net;
using System.Web;
 
namespace TextRecognition
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }
 
        //调用接口所需令牌
        string ACCESS_TOKEN = "";
        //应用的api key
        string API_KEY = "控制台查询";
        //应用的secret key
        string API_SECRET = "控制台查询";
        //存储识别结果
        string resultText = "";
 
        private void MainForm_Load(object sender, EventArgs e)
        {
            getAccessToken();
        }
 
        //获取AccessToken
        private void getAccessToken()
        {
            String authHost = "https://aip.baidubce.com/oauth/2.0/token";
            HttpClient client = new HttpClient();
            List<KeyValuePair<String, String>> paraList = new List<KeyValuePair<string, string>>();
            paraList.Add(new KeyValuePair<string, string>("grant_type", "client_credentials"));
            paraList.Add(new KeyValuePair<string, string>("client_id", API_KEY));
            paraList.Add(new KeyValuePair<string, string>("client_secret", API_SECRET));
 
            HttpResponseMessage response = client.PostAsync(authHost, new FormUrlEncodedContent(paraList)).Result;
            String result = response.Content.ReadAsStringAsync().Result;
 
            //解析返回的json结果
            Dictionary<string, string> res = JsonConvert.DeserializeObject<Dictionary<string, string>>(result);
            res.TryGetValue("access_token", out ACCESS_TOKEN);
        }
        
        //处理识别功能被用户触发
        private void doRecognize()
        {
            IDataObject iData = Clipboard.GetDataObject();
            //只处理复制内容是图片的情况
            if (iData.GetDataPresent(DataFormats.Bitmap))
            {
                var image = Clipboard.GetImage();
                MemoryStream ms = new MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                byte[] arr = new byte[ms.Length];
                ms.Position = 0;
                ms.Read(arr, 0, (int)ms.Length);
                string base64 = Convert.ToBase64String(arr);
                try
                {
                    recognize(base64);
                    //把识别结果复制到剪切板
                    Clipboard.SetText(resultText);
                }
                catch (Exception ex)
                {
                    resultText = "异常：" + ex.ToString(); 
                }
            }
        }
 
        //调用api识别图片中的文字
        private void recognize(string base64)
        {
            string host = "https://aip.baidubce.com/rest/2.0/ocr/v1/accurate_basic?access_token=" + ACCESS_TOKEN;
            Encoding encoding = Encoding.Default;
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(host);
            request.Method = "post";
            request.KeepAlive = true;
            // 图片的base64编码
            String str = "image=" + HttpUtility.UrlEncode(base64);
            byte[] buffer = encoding.GetBytes(str);
            request.ContentLength = buffer.Length;
            request.GetRequestStream().Write(buffer, 0, buffer.Length);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
            string result = reader.ReadToEnd();
            //解析json太麻烦直接正则获取结果
            string pattern = "\"words\":\"(.*?)\"";
            StringBuilder sb = new StringBuilder();
            foreach (Match match in Regex.Matches(result, pattern))
            {
                sb.AppendLine(match.Groups[1].ToString());
            }
            resultText = sb.ToString();
            Console.WriteLine(resultText);
        }
 
    }
}

此时可以在窗口里添加个按钮测试一下doRecognize识别功能，用截图工具截个图，再点按钮，可以看到他已经识别完成并且给我们把结果复制到剪切板了

三、监听快捷键按下

我想实现当按下alt+3的时候执行doReconize函数，需要全局hook键盘。

首先在项目里创建类文件Hook.cs，然后编辑内容

Hook.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace TextRecognition
{
    class Hook
    {
        [DllImport("user32.dll")]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
 
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnhookWindowsHookEx(int idHook);
 
        [DllImport("user32.dll")]
        public static extern int CallNextHookEx(int idHook, int nCode, int wParam, IntPtr lParam);
 
        [DllImport("kernel32.dll")]
        public static extern int GetCurrentThreadId();
 
        [DllImport("kernel32.dll")]
        public static extern IntPtr GetModuleHandle(string name);
 
        [DllImport("User32.dll")]
        public static extern void keybd_event(Byte bVk, Byte bScan, Int32 dwFlags, Int32 dwExtraInfo);
 
        //键盘hook
        public const int WH_KEYBOARD_LL = 13;
        public delegate int HookProc(int nCode, int wParam, IntPtr lParam);
 
        //回调
        HookProc KeyBoardHookProcedure;
 
        public int hHook;
 
        //hook到的消息结构
        [StructLayout(LayoutKind.Sequential)]
        public class KeyBoardHookStruct
        {
            public int vkCode;
            public int scanCode;
            public int flags;
            public int time;
            public int dwExtraInfo;
        }
 
        //开启hook
        public void Hook_Start()
        {
            KeyBoardHookProcedure = new HookProc(KeyBoardHookProc);
            hHook = SetWindowsHookEx(WH_KEYBOARD_LL, KeyBoardHookProcedure, GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), 0);
        }
 
        //关闭hook  
        public void Hook_Clear()
        {
            bool retKeyboard = true;
            retKeyboard = UnhookWindowsHookEx(hHook);
            hHook = 0;
        }
 
        //键盘hook到之后的操作
        private int KeyBoardHookProc(int nCode, int wParam, IntPtr lParam)
        {
            if (nCode >= 0)
            {
                KeyBoardHookStruct kbh = (KeyBoardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyBoardHookStruct));
                //如果按下alt + 3
                if (kbh.vkCode == (int)Keys.D3 && (int)Control.ModifierKeys == (int)Keys.Alt)
                {
                    Console.WriteLine("按了alt+3");
                    //键盘消息不再往下传递
                    return 1;
                }
            }
            return CallNextHookEx(hHook, nCode, wParam, lParam);
        }
    }
}

再来看一下控制台输出，发现可以获取到按下的事件了，如果想换成别的组合键可以上网搜一下该怎么写。

四、按键触发doRecognize函数

我们按下alt+3被hook到之后，要调用MainForm.cs里定义的doRecognize函数。当时学的时候没学太多，只记得个委托什么什么的可以实现这样的功能，我就用这个委托实现了。当然也有别的方式，比如直接抽离成工具类什么的。

我讲不大清楚，大家既然都用c#了应该比我懂得多，我就直接放代码了。

Hook.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace 文字识别
{
    class KeyHooks
    {
        //以下只展示新增or修改的部分
        public delegate void recHandler(object sender, EventArgs e);
 
        public event recHandler handler;
 
        //键盘hook到之后的操作
        private int KeyBoardHookProc(int nCode, int wParam, IntPtr lParam)
        {
            if (nCode >= 0)
            {
                KeyBoardHookStruct kbh = (KeyBoardHookStruct)Marshal.PtrToStructure(lParam, typeof(KeyBoardHookStruct));
                if (kbh.vkCode == (int)Keys.D3 
                    && (int)Control.ModifierKeys == (int)Keys.Alt 
                    && this.handler != null)
                {
                    Console.WriteLine("按了alt+3");
                    this.handler(this, new EventArgs());
                    return 1;
                }
            }
            return CallNextHookEx(hHook, nCode, wParam, lParam);
        }
    }
}

MainForm.cs

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Windows.Forms;
using Newtonsoft.Json;
using System.Text.RegularExpressions;
using System.IO;
using System.Net;
using System.Web;
 
namespace TextRecognition
{
    public partial class MainForm : Form
    {
        //也只展示新增、修改部分
        private void MainForm_Load(object sender, EventArgs e)
        {
            getAccessToken();
            hook.Hook_Start();
            hook.handler += new Hook.recHandler(handleRec);
        }
 
        public void handleRec(object sender, EventArgs e)
        {
            doRecognize();
        }
    }
}

五、优化

我想让他一直在后台，别给我一启动蹦出一个窗口，我还要避免这个程序重复运行。

1.设置后台运行

首先我们把NotifyIcon这个组件拖入到窗口里，再拖个ContextMenuStrip来配置右键展示的菜单

设置一下NotifyIcon的icon，随便找个xxx.ico文件吧，然后修改Text属性，再把ContextMenuStrip属性修改为刚添加的那个context menu strip，然后这个就能在右下角看到了（这个b水印真烦啊）

再编辑一下ContextMenuStrip，我创建了复制上一次识别结果和退出两个选项，双击他们给他们添加点击事件

        private void copyMenuItem_Click(object sender, EventArgs e)
        {
            Clipboard.SetText(resultText);
        }
 
        private void exitMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
        }

再让窗体隐藏，将主窗体的ShowlnTaskbar属性设为 False,将其 WindowState属性设为 Minimized,程序即可变成后台运行程序。

2.防止重复开启

很简单，在Program.cs里写代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace TextRecognition
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            bool unique;
            Console.WriteLine(Application.ProductName);
            System.Threading.Mutex mutex = new System.Threading.Mutex(true, Application.ProductName, out unique);
            if (!unique)
            {
                MessageBox.Show("请勿重复运行此程序！", "错误", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                return;
            }
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new MainForm());
        }
    }
}

ok了，运行一下玩玩把

转自https://blog.csdn.net/m0_52640724/article/details/126994378

[转]C#写一个后台运行的文字识别工具