main.c

在linux下利用video4linux接口采集单幅图像

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>		/* read */
#include <errno.h>		/* errno */
#include <stdlib.h>
#include <termios.h>
#include <math.h>
#include <sys/fcntl.h>
#include <sys/time.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <string.h>
#include <malloc.h>
#include "v4l.h"
#define norm1 VIDEO_MODE_PAL
#define DEFAULT_PALETTE VIDEO_PALETTE_RGB24
int screen_width=320;
int screen_height=240;
v4l_device vd;
//char v4l_norms[8];

int device_init(char *dev, int channel,int norm)
{
   int i;

   if (dev == NULL) {
      dev = "/dev/video0"; //set to default device
   }

   if (v4l_open(dev, &vd)) {
      return -1;
   } else {
      v4l_grab_init(&vd, screen_width, screen_height); //wake up drivers!
      v4l_close(&vd);
   }

   if (v4l_open(dev, &vd)) return -1;
   if (v4l_get_channels(&vd)) return -1;
   if (v4l_set_norm(&vd, norm)) return -1;
   if (v4l_mmap_init(&vd)) return -1;
   if (v4l_switch_channel(&vd, channel)) return -1;

   printf("%s: initialization OK... %s\n"
            "%d channels\n"
            "%d audios\n\n", dev, vd.capability.name, vd.capability.channels, vd.capability.audios);

   for (i = 0; i < vd.capability.channels; i++) {
      //printf("Channel %d: %s (pp)\n", i, vd.channel[i].name,v4l_norms[vd.channel[i].norm].name);
      printf("Channel %d: %s (pp)\n", i, vd.channel[i].name);
   }

   printf("v4l: mmap's address = %p\n", vd.map);
   printf("v4l: mmap's buffer size = 0x%x\n", vd.mbuf.size);
   printf("v4l: mmap's frames = %d (%d max)\n", vd.mbuf.frames, VIDEO_MAX_FRAME);
   for (i = 0; i < vd.mbuf.frames; i++) {
      printf("v4l: frames %d's offset = 0x%x\n", i, vd.mbuf.offsets[i]);
   }

   //printf("v4l: channel switch to %d (%s)\n", channel, vd.channel[channel].name);

   // start initialize grab
   if (v4l_get_picture(&vd)) return -1;
   if (v4l_set_palette(&vd, DEFAULT_PALETTE)) return -1;
   if (v4l_grab_init(&vd, screen_width, screen_height)) return -1;
   if (v4l_grab_sync(&vd)) return -1;

   return 0;
}
int write_ppm24(char *filename, unsigned char* img, int screen_width, int screen_height) 
{ 
int fp,j,k; 
unsigned char header[16];
unsigned char *p=(unsigned char*)img;
unsigned char rgb[3];
if ((fp = open (filename, O_WRONLY | O_CREAT, 0644)) < 0) {
    printf ("ppm open failed: %d\n", errno);
    exit (1);
//fp = fopen(filename,"w"); 
//if(fp == NULL) 
return -1; 
}
sprintf(header,"P6\n%d %d\n255\n",screen_width, screen_height);
//fprintf(fp,"P6\n%d %d\n255\n",screen_width, screen_height); 
write (fp, header, strlen(header));
//fwrite(img, screen_height, 3*screen_width, fp); 
//p = img;
   for (j=0; j<screen_height; j++) {
    for (k=0; k<screen_width; k++) {
      rgb[2] = *p++;		
      rgb[1] = *p++;		
      rgb[0] = *p++;		
     // p++;			
      write(fp, rgb, 3);
    }
 }

close(fp); 
return 0; 

} 



int main()
{   
  unsigned char *image;
	int wid;
	int heigh;
	wid=screen_width;
	heigh=screen_height;
   if (device_init("/dev/video0",0,norm1) == -1) {
      perror("device_init: failed...");
      exit(1);
   } 
   else {
      printf("OK!\n");
   }
    //v4l_grab_frame(vd,2);
  /*if (device_grab_frame(&vd)==-1)
   {
	   perror(" frame failed");
   }
    //Ok, grab a frame.
   if(v4l_grab_sync(&vd)==-1)
   {
	   perror("device grab failed");
   }
   if (device_next_frame(&vd)==-1)
   {
	   perror(" frame failed");
   }
    //Ok, grab a frame.
   if(v4l_grab_sync(&vd)==-1)
   {
	   perror("device grab failed");
   }
   //Wait until captured.
*/
  image = device_get_address(&vd); 
   if (write_ppm24("rgb24.ppm",image,wid,heigh)==-1){
	   perror("read file failed");
	   exit(1);
   }
   printf("%d\n ",image);
  // free(image);
   return 0;
}