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    #include <stdio.h>  
    #include <stdlib.h>  
    #include <string.h>  
    #include <assert.h>  
      
    #include <getopt.h>             
      
    #include <fcntl.h>               
    #include <unistd.h>  
    #include <errno.h>  
    #include <malloc.h>  
    #include <sys/stat.h>  
    #include <sys/types.h>  
    #include <sys/time.h>  
    #include <sys/mman.h>  
    #include <sys/ioctl.h>  
      
    #include <asm/types.h>           
    #include <linux/videodev2.h>  
      
      
    #define VIDEO_WIDTH 640     
    #define VIDEO_HEIGHT 480    
    #define BUFFER_COUNT 4     
      
    #define CLEAR(x) memset (&(x), 0, sizeof (x))  
      
      
    struct buffer {  
        void *      start;      //记录缓冲帧地址  
        size_t      length;     //一帧的大小  
    };  
      
      
    //pic process---------------------------------------------------------------------------------------------------------------------------------------------------------------  
      
    #pragma pack(1)    
    typedef struct BITMAPFILEHEADER{  
          unsigned short bfType;//位图文件的类型,    
          unsigned long bfSize;//位图文件的大小，以字节为单位    
          unsigned short bfReserved1;//位图文件保留字，必须为0    
          unsigned short bfReserved2;//同上    
          unsigned long bfOffBits;//位图阵列的起始位置，以相对于位图文件   或者说是头的偏移量表示，以字节为单位    
    } BITMAPFILEHEADER;  
    #pragma pack()    
      
    typedef struct BITMAPINFOHEADER{//位图信息头类型的数据结构，用于说明位图的尺寸        
          unsigned long biSize;//位图信息头的长度，以字节为单位    
          unsigned long biWidth;//位图的宽度，以像素为单位    
          unsigned long biHeight;//位图的高度，以像素为单位    
          unsigned short biPlanes;//目标设备的级别,必须为1    
          unsigned short biBitCount;//每个像素所需的位数，必须是1(单色),4(16色),8(256色)或24(2^24色)之一    
          unsigned long biCompression;//位图的压缩类型，必须是0-不压缩，1-BI_RLE8压缩类型或2-BI_RLE4压缩类型之一    
          unsigned long biSizeImage;//位图大小，以字节为单位    
          unsigned long biXPelsPerMeter;//位图目标设备水平分辨率，以每米像素数为单位    
          unsigned long biYPelsPerMeter;//位图目标设备垂直分辨率，以每米像素数为单位    
          unsigned long biClrUsed;//位图实际使用的颜色表中的颜色变址数    
          unsigned long biClrImportant;//位图显示过程中被认为重要颜色的变址数    
    } BITMAPINFOHEADER;  
      
      
    void create_bmp_header(struct BITMAPFILEHEADER * bfh,struct BITMAPINFOHEADER * bih){  
          bfh->bfType = (unsigned short)0x4D42;  
          bfh->bfSize = (unsigned long)(14 + 40 + VIDEO_WIDTH * VIDEO_HEIGHT*3);  
          bfh->bfReserved1 = 0;  
          bfh->bfReserved2 = 0;  
          bfh->bfOffBits = (unsigned long)(14 + 40);  
      
      
          bih->biBitCount = 24;  
          bih->biWidth = VIDEO_WIDTH;  
          bih->biHeight = VIDEO_HEIGHT;  
          bih->biSizeImage = VIDEO_WIDTH * VIDEO_HEIGHT * 3;  
          bih->biClrImportant = 0;  
          bih->biClrUsed = 0;  
          bih->biCompression = 0;  
          bih->biPlanes = 1;  
          bih->biSize = 40;//sizeof(bih);    
          bih->biXPelsPerMeter = 0x00000ec4;  
          bih->biYPelsPerMeter = 0x00000ec4;  
      
         printf("----create bmp header successfully !----\n");  
    }  
      
    void store_bmp(FILE * fd,char * file_name,unsigned char * newBuf,int bmp_len,struct BITMAPFILEHEADER * bfh,struct BITMAPINFOHEADER * bih){  
          
        fd = fopen(file_name, "wb");  
        if (fd < 0) {  
                printf("open frame data file failed\n");  
                return;  
        }  
        fwrite(bfh,sizeof(*bfh),1,fd);  
        fwrite(bih,sizeof(*bih),1,fd);  
        fwrite(newBuf, 1, bmp_len, fd);  
        fclose(fd);  
        printf("----store bmp successfuylly ,bmp name is :  %s----\n", file_name);  
        return;  
    }  
      
    /* 
    * YUYV 转 RGB 算法 
    */  
      
    void yuyv2rgb(unsigned int index, struct buffer * buffers,unsigned char * newBuf){  
        unsigned char YUYV[4],RGB[6];  
            int j,k,i;  
        unsigned int location  = 0;  
        unsigned char * starter;  
          
        starter                = (unsigned char *)buffers[index].start;  /* starter 代表当前数据帧在用户空间的首地址*/  
        j=0;  
            for(i=0;i < buffers[index].length;i+=4){  
            YUYV[0]=starter[i];//Y0    
            YUYV[1]=starter[i+1];//U    
            YUYV[2]=starter[i+2];//Y1    
            YUYV[3]=starter[i+3];//V    
            if(YUYV[0]<1){     
                RGB[0]=0;  
                RGB[1]=0;  
                RGB[2]=0;  
            }else{  
                RGB[0]=YUYV[0]+1.772*(YUYV[1]-128);//b    
                RGB[1]=YUYV[0]-0.34413*(YUYV[1]-128)-0.71414*(YUYV[3]-128);//g    
                RGB[2]=YUYV[0]+1.402*(YUYV[3]-128);//r    
            }     
            if(YUYV[2]<0){     
                RGB[3]=0;  
                RGB[4]=0;  
                RGB[5]=0;  
            }else{  
                RGB[3]=YUYV[2]+1.772*(YUYV[1]-128);//b    
                RGB[4]=YUYV[2]-0.34413*(YUYV[1]-128)-0.71414*(YUYV[3]-128);//g    
                RGB[5]=YUYV[2]+1.402*(YUYV[3]-128);//r    
            }  
            for(k=0;k<6;k++){  
                if(RGB[k]<0)  
                    RGB[k]=0;  
                if(RGB[k]>255)  
                    RGB[k]=255;  
            }         
            //请记住：扫描行在位图文件中是反向存储的！    
            if(j%(VIDEO_WIDTH*3)==0){//定位存储位置  
                location=(VIDEO_HEIGHT-j/(VIDEO_WIDTH*3))*(VIDEO_WIDTH*3);  
            }  
            bcopy(RGB,newBuf+location+(j%(VIDEO_WIDTH*3)),sizeof(RGB));  
            j+=6;  
            }  
        printf("---- yuyv 2 rgb CHANGE DONE ! ----");  
        return;  
    }  
      
    /* 
     *去噪算法 
    */  
    void move_noise(unsigned char * newBuf){//双滤波器    
        int i,j,k,temp[3],temp1[3];  
        unsigned char BGR[13*3];  
        unsigned int sq,sq1,loc,loc1;  
        int h=VIDEO_HEIGHT,w=VIDEO_WIDTH;  
      
        for(i=2;i<h-2;i++){  
            for(j=2;j<w-2;j++){  
                memcpy(BGR,newBuf+(i-1)*w*3+3*(j-1),9);  
                memcpy(BGR+9,newBuf+i*w*3+3*(j-1),9);  
                memcpy(BGR+18,newBuf+(i+1)*w*3+3*(j-1),9);  
                memcpy(BGR+27,newBuf+(i-2)*w*3+3*j,3);  
                memcpy(BGR+30,newBuf+(i+2)*w*3+3*j,3);  
                memcpy(BGR+33,newBuf+i*w*3+3*(j-2),3);  
                memcpy(BGR+36,newBuf+i*w*3+3*(j+2),3);  
                  
                memset(temp,0,4*3);  
                for(k=0;k<9;k++){  
                    temp[0]+=BGR[k*3];  
                    temp[1]+=BGR[k*3+1];  
                    temp[2]+=BGR[k*3+2];  
                }  
      
                temp1[0]=temp[0];  
                temp1[1]=temp[1];  
                temp1[2]=temp[2];  
                  
                for(k=9;k<13;k++){  
                    temp1[0]+=BGR[k*3];  
                    temp1[1]+=BGR[k*3+1];  
                    temp1[2]+=BGR[k*3+2];  
                }  
      
                for(k=0;k<3;k++){  
                    temp[k]/=9;  
                    temp1[k]/=13;  
                }  
          
                sq=0xffffffff;loc=0;  
                sq1=0xffffffff;loc1=0;  
                unsigned int a;  
                  
                for(k=0;k<9;k++){  
                    a=abs(temp[0]-BGR[k*3])+abs(temp[1]-BGR[k*3+1])+abs(temp[2]-BGR[k*3+2]);  
                    if(a<sq){  
                        sq=a;  
                        loc=k;  
                    }  
                }  
                for(k=0;k<13;k++){  
                    a=abs(temp1[0]-BGR[k*3])+abs(temp1[1]-BGR[k*3+1])+abs(temp1[2]-BGR[k*3+2]);  
                    if(a<sq1){  
                        sq1=a;  
                        loc1=k;  
                    }  
                }  
                newBuf[i*w*3+3*j]=(unsigned char)((BGR[3*loc]+BGR[3*loc1])/2);  
                        newBuf[i*w*3+3*j+1]=(unsigned char)((BGR[3*loc+1]+BGR[3*loc1+1])/2);  
                            newBuf[i*w*3+3*j+2]=(unsigned char)((BGR[3*loc+2]+BGR[3*loc1+2])/2);  
                         /*还是有些许的噪点   
                temp[0]=(BGR[3*loc]+BGR[3*loc1])/2;   
                    temp[1]=(BGR[3*loc+1]+BGR[3*loc1+1])/2;   
                    temp[2]=(BGR[3*loc+2]+BGR[3*loc1+2])/2;   
                    sq=abs(temp[0]-BGR[loc*3])+abs(temp[1]-BGR[loc*3+1])+abs(temp[2]-BGR[loc*3+2]);   
                    sq1=abs(temp[0]-BGR[loc1*3])+abs(temp[1]-BGR[loc1*3+1])+abs(temp[2]-BGR[loc1*3+2]);   
                    if(sq1<sq) loc=loc1;   
                    newBuf[i*w*3+3*j]=BGR[3*loc];   
                    newBuf[i*w*3+3*j+1]=BGR[3*loc+1];   
                    newBuf[i*w*3+3*j+2]=BGR[3*loc+2];*/  
            }  
            }  
        printf("----move noise successfully---- !\n");  
            return;  
    }  
      
    //end of pic process------------------------------------------------------------------------------------------------------------------------------------------------------  
      
      
    //v4l2 -------------------------------------------------------------------------------------------------------------------------------------------------------------------  
      
    /* 
    查询设备能力，v4l2 规定这一步是必须（暂时这里不指定特别的功能） */  
    void do_cap(int fd,struct v4l2_capability * cap ){  
      if( ioctl(fd,VIDIOC_QUERYCAP,cap) != -1 ){  
        printf("  1:  step1:device capbility checed succssfully\n");  
        return;  
      }  
      exit(EXIT_FAILURE);  
    }  
      
      
    /* 
    规定设备帧捕获格式的信息 
    */  
    void init_fmt(struct  v4l2_format  * fmt){  
      CLEAR(*fmt);  
      fmt->type                     = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
      fmt->fmt.pix.width            = VIDEO_WIDTH;  
      fmt->fmt.pix.height           = VIDEO_HEIGHT;  
      fmt->fmt.pix.pixelformat      = V4L2_PIX_FMT_YUYV;           
      fmt->fmt.pix.field            = V4L2_FIELD_INTERLACED;     
      return;  
    }  
    /* 
    设置设备帧捕获格式 
    */  
    void do_set_fmt(int fd,struct  v4l2_format  * fmt){  
        if(ioctl(fd,VIDIOC_S_FMT,fmt) != -1){  
           printf("  2:  Set devic format  succssfully\n");  
           return;  
        }  
        exit(EXIT_FAILURE);  
    }  
      
    /* 
    初始化缓冲帧请求表单 
    */  
    void init_req(struct v4l2_requestbuffers * req){;  
      CLEAR(*req);  
      req->count                   = BUFFER_COUNT;  
      req->type                    = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
      req->memory                  = V4L2_MEMORY_MMAP;  
    }  
      
    /* 
     *发送命令申请缓冲帧 
    */  
    void do_reqBuf(int fd,struct v4l2_requestbuffers * req ){  
      if(ioctl(fd,VIDIOC_REQBUFS,req) != -1){  
           printf("  3:  request buffers successfully \n");  
           return;  
        }  
        exit(EXIT_FAILURE);  
    }  
      
    /* 
     *获得驱动开辟的缓冲区的物理地址，并将此地址映射到用户空间可用的虚拟地址 
    */  
    void process_bufferAddr(int fd,int num, struct buffer * buffers){  
              
        int i;  
      
            for (i = 0; i < num; ++i)  
            {  
               struct v4l2_buffer buf;     
               CLEAR (buf);  
               buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
               buf.memory      = V4L2_MEMORY_MMAP;  
               buf.index       = i;            //记录当前帧是buffers中的第及帧    
      
               if (-1 == ioctl (fd, VIDIOC_QUERYBUF, &buf)){ //获得缓冲帧的物理地址  
                    printf ("VIDIOC_QUERYBUF error\n");  
                    exit(EXIT_FAILURE);  
               }  
               buffers[i].length = buf.length;  
            
               buffers[i].start =            //将内存中缓冲帧的物理地址映射为用户空间地址  
               mmap (NULL,  
                    buf.length,   
                    PROT_READ | PROT_WRITE ,  
                    MAP_SHARED,  
                    fd, buf.m.offset);  
               if (MAP_FAILED == buffers[i].start){  
                    printf ("mmap failed\n");  
            exit(EXIT_FAILURE);  
           }       
            }//end of for  
          
           printf("  4:  address processed successfully! \n");  
           return;  
    }  
      
      
    /* 
     *操作内存中已开辟好空间的缓冲帧入队列，准备记录数据信息 
    */  
    void in_queue(int fd, int num){  
        int i;  
        for(i = 0; i < num; ++i){  
            struct v4l2_buffer buf;         //工作数据帧，用户填好index和type字段后，传给驱动，驱动根据这些信息去处理内存中实际存在的数据帧  
            CLEAR(buf);  
            buf.index     =  i;  
            buf.type      =  V4L2_BUF_TYPE_VIDEO_CAPTURE;  
            buf.memory    = V4L2_MEMORY_MMAP;  
                  
                if(-1 == ioctl(fd, VIDIOC_QBUF,&buf)){  
                printf("VIDIOC_QBUF error !\n");  
                exit(EXIT_FAILURE);  
            }  
        }  
          
            printf("  5:  in queue successfully !\n");  
        return;  
    }  
      
      
    /* 
     *开始采集数据  
    */  
    void do_capture(int fd){  
        enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        if( -1 == ioctl(fd,VIDIOC_STREAMON,&type)){  
            printf("VIDIOC_STREAMON error ! \n");  
            exit(EXIT_FAILURE);  
        }  
          
            printf("  6:  do capture  successfully !\n");  
        return;  
    }  
      
    /* 
     *将数据帧存储为jpg图片 
    */  
      
    void save_asJpg(__u32 index, struct buffer * buffers){  
          
        /* 
               采集到的图片相关的变量 
            */  
            FILE *           pic_fd;                    //图片文件描述符  
            unsigned long    pic_length;                        //文件大小  
            char *           pic_fileName        = "test.jpg";      //图像文件名  
      
        pic_fd = fopen(pic_fileName,"wb");  
        fwrite(buffers[index].start, buffers[index].length, 1,pic_fd);  
          
        fclose(pic_fd);                                         /*关闭文件*/  
          
            printf("----  save pic as jpg  successfully !----\n");  
        return;  
    }  
      
    void save_asBmp(unsigned int index, struct buffer * buffers){  
      
        FILE *         bmp_fd;         /*新创建的bmp文件的文件描述副*/  
        char *         bmp_name =  "testBMP.bmp";  
      
        unsigned char * bmpBuf;        /*为了处理jpg 转 bmp ，需要在内存中开辟一段工作空间*/  
        int bmp_len;                   /*bmp 图片大小*/  
              
        struct BITMAPFILEHEADER bfh;   /*bmp 文件结构体*/  
        struct BITMAPINFOHEADER bih;     
      
        bmp_len         =  buffers[index].length*3/2;  
            bmpBuf          =  calloc((unsigned int)bmp_len,sizeof(unsigned char));  
          
            if(!bmpBuf){  
             printf("cannot assign the memory for bmp!\n");  
                 exit(EXIT_FAILURE);  
            }  
      
        yuyv2rgb(index,buffers,bmpBuf);   /*将 buffers[index]代表的jpg格式的数据转换成bmp格式*/  
          
        move_noise(bmpBuf);  
          
        create_bmp_header(&bfh,&bih);  
        store_bmp(bmp_fd,bmp_name,bmpBuf,bmp_len,&bfh,&bih);  
          
    }  
      
    /* 
     * 将一帧放入数据缓冲队列 
    */  
    int put_oneFrame_inQue(int camera_fd,struct v4l2_buffer * buf){  
        ioctl(camera_fd,VIDIOC_QBUF,buf);  
        return buf->index;  
    }  
      
    /* 
    *此函数由monitor_queue 函数调用，用来从设备文件中读取视频数据 
    */  
    int read_frame (int camera_fd,struct buffer * buffers)  
    {  
        struct v4l2_buffer buf;  
        unsigned int i;  
      
        CLEAR (buf);  
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
        buf.memory = V4L2_MEMORY_MMAP;  
      
        ioctl (camera_fd, VIDIOC_DQBUF, &buf);       /*从数据缓冲队列中取出数据帧*/  
      
        //assert (buf.index < num);     
          
        save_asJpg(buf.index,buffers);              /* 将读取到的帧存为jpg格式的图片  */  
          
        save_asBmp(buf.index,buffers);  
      
        put_oneFrame_inQue(camera_fd,&buf);         /*重新把帧插入队列*/  
      
            printf("  7:  read frame  successfully !\n");  
        return 1;  
    }  
      
      
    /* 
    *监听数据队列数据帧的状态，状态发生改变（说明采集到了数据）,则调用read_frame函数返回数据帧 
    */  
    void monitor_queue(int fd,struct buffer * buffers){  
          
        while (1)   
            {  
               fd_set fds;           //为select函数设置监听文件集，即：fds文件集合中的所有文件的状态将会被监听  
               struct timeval tv;    //设置等待超时时间  
               int ret;  
      
               FD_ZERO (&fds);  
               FD_SET (fd, &fds);  
      
               /* Timeout. */  
               tv.tv_sec = 2;  
               tv.tv_usec = 0;  
      
               ret = select (fd + 1, &fds, NULL, NULL, &tv);  
                
               //监听出错  
               if (-1 == ret) {  
                 if (EINTR == errno)  
                         continue;  
                     printf ("select err\n");  
               }  
           //等待超时  
               if (0 == ret) {  
                fprintf (stderr, "select timeout\n");  
                    exit (EXIT_FAILURE);  
               }  
               //当ret != -1 && != 0时，则ret的值表示状态改变的文件个数  
               if (read_frame (fd,buffers))  
                    break;  
            }   
      
            printf("  8:  do capture  successfully !\n");  
        return;  
    }  
      
      
      
    /* 
     *将mmap映射的地址空间还原 
    */  
      
    void release_mmap_buffer(int num,struct buffer * buffers){  
      
        int i;  
      
        for (i = 0; i < num; ++i){  
            if (-1 == munmap (buffers[i].start, buffers[i].length)){  
                printf ("munmap error !\n");  
                exit(EXIT_FAILURE);  
            }  
        }  
        printf("  9:  mmap buffer released successfuly !\n");  
        return;  
    }  
    /* 
    初始化程序的上下s，然后开始视频采s 
     */  
    void init_context(){  
        /* 
           摄像头设备相关变量  
            */  
        char *          camera_fileName      = "/dev/video0";   // linux下摄像头设备的文件名  
        int             camera_fd            = -1;              // 摄像头的文件描述符  
          
        /* 
             视频采集相关变量               
            */  
        struct v4l2_capability   cap;                  //查询设备的能力  
            struct v4l2_format       fmt;                  //设置设备当前驱动的帧捕获格式  
            enum   v4l2_buf_type     type;                 //定义设备的采集方式  
        struct v4l2_requestbuffers req;  
          
            struct buffer *          buffers;              //向系统内存申请缓冲区，用于在内存中保存数据帧信息  
      
        /* 
         * 图片采集处理相关变量 
        */  
            unsigned char *          bmp_picBuf;  
        int              bmp_len;  
      
      
        /* 
             启动采集工作 
           */  
      
        //以阻塞方式打开一个设备文件  
        camera_fd = open(camera_fileName,O_RDWR,0);    
            
            //1、v4l2 规定此步必须有  
            do_cap(camera_fd,&cap);  
              
            //2、设置设备捕获数据格式  
            init_fmt(&fmt);  
            do_set_fmt(camera_fd,&fmt);  
              
            //3、申请缓冲区  
            init_req(&req);  
            do_reqBuf(camera_fd,&req);  
              
        //4、获得缓冲帧地址，并且将其映射到用户空间        
            buffers = calloc (req.count, sizeof (*buffers));   //系统为为应用程序分配缓冲区，并清零  
            process_bufferAddr(camera_fd,req.count,buffers);   //处理地址问题，函数返回后，buffers中即可获得缓冲帧的虚拟地址（应用程序可操作）   
      
        //5、通知驱动把内存中的数据帧入队，准备记录数据信息  
        in_queue(camera_fd,req.count);  
      
        //6、通知驱动开始视频采集  
        do_capture(camera_fd);    
          
        //7、监听数据队列，并从队列中取出数据帧  
        monitor_queue(camera_fd,buffers);  
      
        //8、图片处理  
      
      
      
            //9、*  
        /* 解除地址映射 */  
        release_mmap_buffer(req.count,buffers);   
        /* 关闭设备文件*/  
            close(camera_fd);  
        /* 关闭图像文件*/  
    }  
      
    void main(){  
      init_context();  
    }  


这里的例子程序摘自网络，为了方便像我一样的新手阅读，小人斗胆对每一行加了注释，错误难免，欢迎大家留言更正。我会在第一时间更新。光荣属于前辈和你们。