YUYV摄像头采集jpeg格式图片

PC系统：ubuntu10.04
gcc版本：4.5.1
视频协议：V4L2
jpeg压缩库：libjpeg
以上都是开源的，下载安装教程很多，不再赘述

说明：（1）由于libjpeg库的例程中，输入的是RGB24格式的图像，而摄像头只能采集YUYV（YUV：422）格式数据，所以，程序中，有YUYV转换为RGB24的过程，再输入libjpeg中
         （2）关于yuyv与rgb24的格式，网上资料很多，自行查阅资料
         （3）libjpeg库的输出只能是一个文件，如需将输出到内存中，需要修改libjpeg（这个还不会）
   

程序如下：

#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>#include <sys/ioctl.h>#include <stdlib.h>#include <sys/mman.h>#include <linux/types.h>#include <linux/videodev2.h>#include <setjmp.h>#include "jpeglib.h" //#include "v4l2grab.h"typedef int BOOL;#define  TRUE    1#define  FALSE    0#define FILE_VIDEO     "/dev/video0"//#define BMP          "image_bmp.bmp"#define YUV        "image_yuv.yuv"#define JPEG        "image_jpeg.jpg"#define  IMAGEWIDTH    320#define  IMAGEHEIGHT   240static   int      fd;static   struct   v4l2_capability   cap;struct v4l2_fmtdesc fmtdesc;struct v4l2_format fmt,fmtack;struct v4l2_streamparm setfps;  struct v4l2_requestbuffers req;struct v4l2_buffer buf;enum v4l2_buf_type type;unsigned char frame_buffer[IMAGEWIDTH*IMAGEHEIGHT*3];struct buffer{    void * start;    unsigned int length;} * buffers; int init_v4l2(void){    int i;    int ret = 0;        //opendev    if ((fd = open(FILE_VIDEO, O_RDWR)) == -1)     {        printf("Error opening V4L interface\n");        return (FALSE);    }    //query cap    if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1)     {        printf("Error opening device %s: unable to query device.\n",FILE_VIDEO);        return (FALSE);    }    else    {         printf("driver:\t\t%s\n",cap.driver);         printf("card:\t\t%s\n",cap.card);         printf("bus_info:\t%s\n",cap.bus_info);         printf("version:\t%d\n",cap.version);         printf("capabilities:\t%x\n",cap.capabilities);                  if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == V4L2_CAP_VIDEO_CAPTURE)          {            printf("Device %s: supports capture.\n",FILE_VIDEO);        }        if ((cap.capabilities & V4L2_CAP_STREAMING) == V4L2_CAP_STREAMING)         {            printf("Device %s: supports streaming.\n",FILE_VIDEO);        }    }         //emu all support fmt    fmtdesc.index=0;    fmtdesc.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;    printf("Support format:\n");    while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc)!=-1)    {        printf("\t%d.%s\n",fmtdesc.index+1,fmtdesc.description);        fmtdesc.index++;    }        //set fmt        fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;    fmt.fmt.pix.height = IMAGEHEIGHT;    fmt.fmt.pix.width = IMAGEWIDTH;    fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;        if(ioctl(fd, VIDIOC_S_FMT, &fmt) == -1)    {        printf("Unable to set format\n");        return FALSE;    }         if(ioctl(fd, VIDIOC_G_FMT, &fmt) == -1)    {        printf("Unable to get format\n");        return FALSE;    }     {         printf("fmt.type:\t\t%d\n",fmt.type);         printf("pix.pixelformat:\t%c%c%c%c\n",fmt.fmt.pix.pixelformat & 0xFF, (fmt.fmt.pix.pixelformat >> 8) & 0xFF,(fmt.fmt.pix.pixelformat >> 16) & 0xFF, (fmt.fmt.pix.pixelformat >> 24) & 0xFF);         printf("pix.height:\t\t%d\n",fmt.fmt.pix.height);         printf("pix.width:\t\t%d\n",fmt.fmt.pix.width);         printf("pix.field:\t\t%d\n",fmt.fmt.pix.field);    }    //set fps    setfps.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    setfps.parm.capture.timeperframe.numerator = 10;    setfps.parm.capture.timeperframe.denominator = 10;        printf("init %s \t[OK]\n",FILE_VIDEO);            return TRUE;}int v4l2_grab(void){    unsigned int n_buffers;        //request for 4 buffers     req.count=4;    req.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;    req.memory=V4L2_MEMORY_MMAP;    if(ioctl(fd,VIDIOC_REQBUFS,&req)==-1)    {        printf("request for buffers error\n");    }    //mmap for buffers    buffers = malloc(req.count*sizeof (*buffers));    if (!buffers)     {        printf ("Out of memory\n");        return(FALSE);    }        for (n_buffers = 0; n_buffers < req.count; n_buffers++)     {        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;        buf.memory = V4L2_MEMORY_MMAP;        buf.index = n_buffers;        //query buffers        if (ioctl (fd, VIDIOC_QUERYBUF, &buf) == -1)        {            printf("query buffer error\n");            return(FALSE);        }        buffers[n_buffers].length = buf.length;        //map        buffers[n_buffers].start = mmap(NULL,buf.length,PROT_READ |PROT_WRITE, MAP_SHARED, fd, buf.m.offset);        if (buffers[n_buffers].start == MAP_FAILED)        {            printf("buffer map error\n");            return(FALSE);        }    }            //queue    for (n_buffers = 0; n_buffers < req.count; n_buffers++)    {        buf.index = n_buffers;        ioctl(fd, VIDIOC_QBUF, &buf);    }         type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    ioctl (fd, VIDIOC_STREAMON, &type);        ioctl(fd, VIDIOC_DQBUF, &buf);    printf("grab yuyv OK\n");    return(TRUE);}int yuyv_2_rgb888(void){    int           i,j;    unsigned char y1,y2,u,v;    int r1,g1,b1,r2,g2,b2;    char * pointer;    pointer = buffers[0].start;    for(i=0;i<IMAGEHEIGHT;i++)    {    for(j=0;j<IMAGEWIDTH/2;j++)//每次取4个字节，也就是两个像素点，转换rgb，6个字节，还是两个像素点    {    y1 = *( pointer + (i*IMAGEWIDTH/2+j)*4);         u  = *( pointer + (i*IMAGEWIDTH/2+j)*4 + 1);    y2 = *( pointer + (i*IMAGEWIDTH/2+j)*4 + 2);    v  = *( pointer + (i*IMAGEWIDTH/2+j)*4 + 3);    r1 = y1 + 1.042*(v-128);    g1 = y1 - 0.34414*(u-128) - 0.71414*(v-128);    b1 = y1 + 1.772*(u-128);    r2 = y2 + 1.042*(v-128);    g2 = y2 - 0.34414*(u-128) - 0.71414*(v-128);    b2 = y2 + 1.772*(u-128);    if(r1>255)    r1 = 255;    else if(r1<0)    r1 = 0;    if(b1>255)    b1 = 255;    else if(b1<0)    b1 = 0;        if(g1>255)    g1 = 255;    else if(g1<0)    g1 = 0;        if(r2>255)    r2 = 255;    else if(r2<0)    r2 = 0;    if(b2>255)    b2 = 255;    else if(b2<0)    b2 = 0;        if(g2>255)    g2 = 255;    else if(g2<0)    g2 = 0;            *(frame_buffer + (i*IMAGEWIDTH/2+j)*6    ) = (unsigned char)b1;    *(frame_buffer + (i*IMAGEWIDTH/2+j)*6 + 1) = (unsigned char)g1;    *(frame_buffer + (i*IMAGEWIDTH/2+j)*6 + 2) = (unsigned char)r1;    *(frame_buffer + (i*IMAGEWIDTH/2+j)*6 + 3) = (unsigned char)b2;    *(frame_buffer + (i*IMAGEWIDTH/2+j)*6 + 4) = (unsigned char)g2;    *(frame_buffer + (i*IMAGEWIDTH/2+j)*6 + 5) = (unsigned char)r2;    }    }    printf("change to RGB OK \n");}BOOL encode_jpeg(char *lpbuf,int width,int height){    struct jpeg_compress_struct cinfo ;    struct jpeg_error_mgr jerr ;    JSAMPROW  row_pointer[1] ;    int row_stride ;    char *buf=NULL ;    int x ;    FILE *fptr_jpg = fopen (JPEG,"wb");//注意这里为什么用fopen而不用open    if(fptr_jpg==NULL)    {    printf("Encoder:open file failed!/n") ;     return FALSE;    }    cinfo.err = jpeg_std_error(&jerr);    jpeg_create_compress(&cinfo);    jpeg_stdio_dest(&cinfo, fptr_jpg);    cinfo.image_width = width;    cinfo.image_height = height;    cinfo.input_components = 3;    cinfo.in_color_space = JCS_RGB;    jpeg_set_defaults(&cinfo);    jpeg_set_quality(&cinfo, 80,TRUE);    jpeg_start_compress(&cinfo, TRUE);    row_stride = width * 3;    buf=malloc(row_stride) ;    row_pointer[0] = buf;    while (cinfo.next_scanline < height)    {     for (x = 0; x < row_stride; x+=3)    {    buf[x]   = lpbuf[x];    buf[x+1] = lpbuf[x+1];    buf[x+2] = lpbuf[x+2];    }    jpeg_write_scanlines (&cinfo, row_pointer, 1);//critical    lpbuf += row_stride;    }    jpeg_finish_compress(&cinfo);    fclose(fptr_jpg);    jpeg_destroy_compress(&cinfo);    free(buf) ;    return TRUE ;}  int close_v4l2(void){     if(fd != -1)      {         close(fd);         return (TRUE);     }     return (FALSE);}int main(void){    FILE * fp2;    if(init_v4l2() == FALSE)     {    return(FALSE);    }    v4l2_grab();    yuyv_2_rgb888();                  //yuyv to RGB24    encode_jpeg(frame_buffer,IMAGEWIDTH,IMAGEHEIGHT); //RGB24 to Jpeg    printf("save "JPEG"OK\n");    close_v4l2();    return(TRUE);}

参考博文：
http://www.cnblogs.com/surpassal/archive/2012/12/19/zed_webcam_lab1.html
http://blog.csdn.net/xingyu19871124/article/details/5517796