C# 实现SDL2进行视频播放窗口截图和字幕添加

使用SDL2进行视频播放窗口截图和字幕添加操作

SDL API查看：https://wiki.libsdl.org/APIByCategory

视频截图

我就废话不多说了，大家还是直接看代码吧~

 /// <summary>
 /// SDL2截图操作类
 /// </summary>
 public unsafe class SDLScreenshot
 {
  IntPtr window;// 窗口对象
  IntPtr renderer;// 播放窗口的渲染器（来自于已初始化的播放窗口渲染器）
  public SDLScreenshot(IntPtr window, IntPtr renderer)
  {
   this.window = window;
   this.renderer = renderer;
  }
  /// <summary>
  /// 保存截图
  /// </summary>
  /// <param name="width"></param>
  /// <param name="height"></param>
  /// <param name="path"></param>
  public void SaveBMP(int width, int height,string path)
  {
   // 判断渲染器是否初始化
   if (renderer == IntPtr.Zero)
   {
    Console.WriteLine("renderer is null ,please call Init() method.");
    return;
   }
   uint Rmask=0x00FF0000, Gmask = 0x0000FF00, Bmask = 0x000000FF, Amask = 0x00000000;
   // 获取图像数据
   SDL.SDL_Surface* surface= (SDL.SDL_Surface*)SDL.SDL_CreateRGBSurface(0, width, height, 32, Rmask, Gmask, Bmask, Amask);
   //设置纹理的数据
   SDL.SDL_Rect destrect;
   destrect.x = 0;
   destrect.y = 0;
   destrect.w = width;
   destrect.h = height; 

   // 读取并渲染图像数据
   SDL.SDL_RenderReadPixels(renderer, ref destrect, SDL.SDL_PIXELFORMAT_ARGB8888, surface->pixels, surface->pitch); 

   //保存图片
   int i = SDL.SDL_SaveBMP((IntPtr)surface, path);
   if (i != 0)
   {
    Console.WriteLine("screenshot failed." + SDL.SDL_GetError());
   } 

   SDL.SDL_FreeSurface((IntPtr)surface);
   //SDL.SDL_RenderClear(renderer);
   //SDL.SDL_DestroyRenderer(renderer);
  } 

  /// <summary>
  /// 加载截图
  /// </summary>
  /// <param name="width"></param>
  /// <param name="height"></param>
  /// <param name="path"></param>
  public void LoadBMP(int width, int height, string path)
  {
   // 判断渲染器是否初始化
   if (renderer == IntPtr.Zero)
   {
    Console.WriteLine("renderer is null ,please call Init() method.");
    return;
   }
   // 加载图片
   IntPtr surface = SDL.SDL_LoadBMP(path);
   if (surface == IntPtr.Zero)
   {
    Console.WriteLine("load bmp failed." + SDL.SDL_GetError());
    return;
   }
   IntPtr texture = SDL.SDL_CreateTextureFromSurface(renderer, surface);
   if (texture == IntPtr.Zero)
   {
    Console.WriteLine("create texture failed." + SDL.SDL_GetError());
    return;
   }
   SDL.SDL_FreeSurface(surface); 

   //设置纹理的数据
   SDL.SDL_Rect destrect;
   destrect.x = 0;
   destrect.y = 0;
   destrect.w = width;
   destrect.h = height; 

   SDL.SDL_Rect srcrect = destrect; 

   //SDL.SDL_RenderClear(renderer);
   SDL.SDL_RenderCopy(renderer, texture, ref srcrect, ref destrect);
   SDL.SDL_RenderPresent(renderer);

   //SDL.SDL_Delay(20);
   SDL.SDL_DestroyTexture(texture);
   //SDL.SDL_DestroyRenderer(renderer);
   //SDL.SDL_DestroyWindow(screen);
   //Quit SDL
   //SDL.SDL_Quit();
  }
 }

播放测试代码：

 if (isSaveScreenshot)
       {
        SDLScreenshot screenshot = new SDLScreenshot(sdlVideo.window, sdlVideo.sdlrenderer);
        screenshot.SaveBMP(nvVideoframe.VideoFrame->width, nvVideoframe.VideoFrame->height, "screenshot.bmp");
        isSaveScreenshot = false;
     }

测试效果图：

注：此处截图是直接获取的播放窗口的图像像素来实现的。

视频字幕

 /// <summary>
 /// SDL2字幕显示类
 /// </summary>
 public unsafe class SDLTTF
 {
  IntPtr renderer;// 播放窗口的渲染器（来自于已初始化的播放窗口渲染器）

  public SDLTTF(IntPtr renderer)
	{
   this.renderer = renderer;
  }

  /// <summary>
  /// 展示字幕文字
  /// </summary>
  /// <param name="text"></param>
  public void ShowText(string ttfPath, int fontSize,string text)
  {
   // 初始化 ttf
   if (SDL_ttf.TTF_Init() < 0)
   {
    Console.WriteLine("SDL_ttf.TTF_Init() failed.");
    return;
   }
   // 是否初始化完成
   int was_init = SDL_ttf.TTF_WasInit();

   if (was_init == 1)
    // SDL_ttf was already initialized
    Console.WriteLine("SDL_ttf was already initialized");
   else if (was_init == 0)
    // SDL_ttf was not already initialized
    Console.WriteLine("SDL_ttf was not already initialized");

   // 判断是否初始化
   if (renderer == IntPtr.Zero)
   {
    Console.WriteLine("Not initialized by SDL_ttf.TTF_Init() ,please call Init() method.");
    return;
   }

   //如：打开ttfPath=simfang.ttf 字库，设字体为fontSize=20号
   IntPtr font = SDL_ttf.TTF_OpenFont(ttfPath, fontSize);
   if (font == IntPtr.Zero)
   {
    Console.WriteLine("open font failed." + SDL.SDL_GetError());
    return;
   }

   // 设置文字颜色
   SDL.SDL_Color color;
   color.a = 255;
   color.r = 255;
   color.g = 255;
   color.b = 255;

   // 渲染文字效果
   //IntPtr surface = SDL_ttf.TTF_RenderUTF8_Blended(font, text, color);
   IntPtr surface = SDL_ttf.TTF_RenderUNICODE_Blended(font, text, color);
   if (surface == IntPtr.Zero)
   {
    Console.WriteLine("show surface failed." + SDL.SDL_GetError());
   }
   IntPtr texture = SDL.SDL_CreateTextureFromSurface(renderer, surface);
   if (texture == IntPtr.Zero)
   {
    Console.WriteLine("create texture failed." + SDL.SDL_GetError());
   }
   SDL.SDL_FreeSurface(surface);
   // 关闭字体
   SDL_ttf.TTF_CloseFont(font);

   // 停止显示
   SDL_ttf.TTF_Quit();

   //设置纹理的数据
   SDL.SDL_Rect destrect;
   destrect.x = 0;
   destrect.y = 0;
   destrect.w = text.Length * 20;
   destrect.h = 20;

   SDL.SDL_Rect srcrect = destrect;
   SDL.SDL_RenderClear(renderer);
   SDL.SDL_RenderCopy(renderer, texture, ref srcrect, ref destrect);
   SDL.SDL_RenderPresent(renderer);
   SDL.SDL_DestroyTexture(texture);
   SDL.SDL_DestroyRenderer(renderer);
  }
 }

事件测试字幕添加：

需要的引用库下载：https://www.libsdl.org/projects/SDL_ttf/

 /// <summary>
  /// 字幕叠加****需要添加三个dll库：SDL2_ttf.dll 、libfreetype-6.dll 、zlib1.dll
  /// </summary>
  /// <param name="sender"></param>
  /// <param name="e"></param>
  private void mbtnAddFontText_Click(object sender, EventArgs e)
  {
   Console.WriteLine("叠加字幕...............");

   sdlTTF = new SDLTTF(sdlVideo.sdlrenderer);
   // 中英文都需要兼容
   string text = "Hello 世界!";
   // 设置一个字体库并设置字体大小和显示文字内容
   sdlTTF.ShowText("simkai.ttf",12, text);
  }

测试效果图：

如果是播放过程中显示字幕一定要在视频渲染完成后渲染字幕，如下面工具类的方法：

/// <summary>
  /// 播放视频
  /// </summary>
  /// <param name="width"></param>
  /// <param name="height"></param>
  /// <param name="pixels"></param>
  /// <param name="pixelsSize"></param>
  /// <param name="pitch"></param>
  /// <returns></returns>
  public int SDL_Display(int width, int height, IntPtr pixels, int pixelsSize,
   int pitch)
  {
   lock (this)
   {
    while (isPause)
    {
     SDL.SDL_Delay(20);//延迟播放
    }

    #region SDL 视频数据渲染播放
    //设置纹理的数据
    sdlrect.x = 0;
    sdlrect.y = 0;
    sdlrect.w = width;
    sdlrect.h = height;
    SDL.SDL_UpdateTexture(sdltexture, ref sdlrect, pixels, pitch);
    //SDL.SDL_UpdateTexture(sdltexture, IntPtr.Zero, pixels, pitch);//此处代码导致播放窗口绿色阴影
    //复制纹理信息到渲染器目标
    SDL.SDL_RenderClear(sdltexture);
    //SDL.SDL_Rect srcRect = sdlrect;
    //SDL.SDL_RenderCopy(sdlrenderer, sdltexture, ref srcRect, ref sdlrect);

    SDL.SDL_RenderCopy(sdlrenderer, sdltexture, IntPtr.Zero, IntPtr.Zero);
    //字幕渲染显示-特别提醒：此处必须放置于视频渲染之后，否则字幕不会显示
    if (ttfText!=null&&!ttfText.Equals(""))
    {
     RenderToShowTTF(ttfText);
    }
    //else
    //{
    // RenderToShowTTF( "未设置字幕内容");
    //}
    //视频渲染显示
    SDL.SDL_RenderPresent(sdlrenderer);
    //SDL.SDL_Delay(40);
    //SDL.SDL_PollEvent(out sdlevent);
    //switch (sdlevent.type)
    //{
    // case SDL.SDL_EventType.SDL_QUIT:
    //  SDL.SDL_Quit();
    //  return -1;
    // default:
    //  break;
    //}
    return 0;
   } 

   //SDL.SDL_RenderClear(sdlrenderer);
   //SDL.SDL_RenderCopy(sdlrenderer, sdltexture, ref srcRect, ref sdlrect);
   //SDL.SDL_RenderPresent(sdlrenderer);
   Delay 40ms
   //SDL.SDL_Delay(40);
   #endregion 

   //#region SDL 视频数据渲染播放
   //设置纹理的数据
   sdlrect.x = 0;
   sdlrect.y = 0;
   sdlrect.w = width;
   sdlrect.h = height;
   SDL.SDL_UpdateTexture(sdltexture, ref sdlrect, pixels, pitch);
   //复制纹理信息到渲染器目标
   SDL.SDL_Rect srcRect = sdlrect;
   SDL.SDL_RenderCopy(sdlrenderer, sdltexture, ref srcRect, ref sdlrect);
   //视频渲染显示
   SDL.SDL_RenderPresent(sdlrenderer);
   //SDL.SDL_Delay(40);
   SDL.SDL_PollEvent(out sdlevent);
   switch (sdlevent.type)
   {
    case SDL.SDL_EventType.SDL_QUIT:
     SDL.SDL_Quit();
     return -1;
    default:
     break;
   }
   return 0;
   //#endregion
  }

  /// <summary>
  /// 设置字幕显示内容
  /// </summary>
  /// <param name="ttfPath"></param>
  /// <param name="fontSize"></param>
  public void SDL_TTF_TEXT(string ttfPath, string text, int fontSize)
  {
   this.ttfPath = ttfPath;
   this.ttfText = text;
   this.ttfFontSize = fontSize;
  }

  /// <summary>
  /// 渲染字幕
  /// </summary>
  /// <param name="text"></param>
  private void RenderToShowTTF(string text)
  {
   // 初始化 ttf
   if (SDL_ttf.TTF_Init() < 0)
   {
    Console.WriteLine("SDL_ttf.TTF_Init() failed.");
    return;
   }
   // 是否初始化完成
   int was_init = SDL_ttf.TTF_WasInit();

   if (was_init == 1)
    // SDL_ttf was already initialized
    Console.WriteLine("SDL_ttf was already initialized");
   else if (was_init == 0)
    // SDL_ttf was not already initialized
    Console.WriteLine("SDL_ttf was not already initialized");

   //如：打开ttfPath=simfang.ttf 字库，设字体为fontSize=20号
   IntPtr font = SDL_ttf.TTF_OpenFont(ttfPath, ttfFontSize);
   if (font == IntPtr.Zero)
   {
    Console.WriteLine("open font failed." + SDL.SDL_GetError());
    return;
   }

   // 设置文字字体
   SDL_ttf.TTF_SetFontStyle(font, SDL_ttf.TTF_STYLE_BOLD);

   // 设置文字颜色
   SDL.SDL_Color color;
   color.a = 255;
   color.r = 255;
   color.g = 255;
   color.b = 255;

   // 渲染文字效果
   //IntPtr surface = SDL_ttf.TTF_RenderText_Blended(font, text, color);
   IntPtr surface = SDL_ttf.TTF_RenderUTF8_Blended(font, text, color);
   //IntPtr surface = SDL_ttf.TTF_RenderUNICODE_Blended(font, text, color);
   if (surface == IntPtr.Zero)
   {
    Console.WriteLine("show surface failed." + SDL.SDL_GetError());
   }
   IntPtr texture = SDL.SDL_CreateTextureFromSurface(sdlrenderer, surface);
   if (texture == IntPtr.Zero)
   {
    Console.WriteLine("create texture failed." + SDL.SDL_GetError());
   }

   SDL.SDL_FreeSurface(surface);
   // 关闭字体
   SDL_ttf.TTF_CloseFont(font);

   // 停止显示
   SDL_ttf.TTF_Quit();

   // 计算合适的宽度和高度
   int texWidth = 0;
   int texHeight = 0;
   uint format = 0;
   int access = 0;
   // 下面这行代码解决字体虚浮不清问题
   SDL.SDL_QueryTexture(texture, out format, out access, out texWidth, out texHeight);
   //设置纹理的数据
   SDL.SDL_Rect destrect;
   destrect.x = 0;
   destrect.y = 0;
   destrect.w = texWidth;
   destrect.h = texHeight;

   SDL.SDL_Rect srcrect = destrect;
   SDL.SDL_RenderCopy(sdlrenderer, texture, ref srcrect, ref destrect);
  }

效果就会好很多：

请看这里的“中华人民共和国”

注意：

常用中英文ttf字体包中包含了：times new roman，中山行书百年纪念版，calibri，Christopherhand，DejaVuSansMono，方正兰亭黑，James Fajardo，Monaco，微软雅黑，仿宋，黑体，楷体，宋体，yahei_mono，仿宋_GB2312，楷体_GB2312，迷你简行楷碑等。

本文使用的是simkai.ttf。

下面是部分字体文件名：

bb1550.ttf

calibri.ttf

calibrib.ttf

calibrii.ttf

calibriz.ttf

comesinhandy.ttf

DejaVuSansMono-Bold.ttf

DejaVuSansMono-BoldOblique.ttf

DejaVuSansMono-Oblique.ttf

DejaVuSansMono.ttf

DroidSansFallback.ttf

James_Fajardo.ttf

Monaco.ttf

msyh.ttf

msyhbd.ttf

simfang.ttf

simhei.ttf

simkai.ttf

simsun.ttc

times.ttf

timesbd.ttf

timesbi.ttf

timesi.ttf

yahei_mono.ttf

如果懒得下载，Windows里面有字体，在C:\Windows\Fonts目录下。

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