WSL2-Linux-Kernel/Documentation/video4linux/v4lgrab.c

/* Simple Video4Linux image grabber. */
/*
 *	Video4Linux Driver Test/Example Framegrabbing Program
 *
 *	Compile with:
 *		gcc -s -Wall -Wstrict-prototypes v4lgrab.c -o v4lgrab
 *	Use as:
 *		v4lgrab >image.ppm
 *
 *	Copyright (C) 1998-05-03, Phil Blundell <philb@gnu.org>
 *	Copied from http://www.tazenda.demon.co.uk/phil/vgrabber.c
 *	with minor modifications (Dave Forrest, drf5n@virginia.edu).
 *
 *
 *	For some cameras you may need to pre-load libv4l to perform
 *	the necessary decompression, e.g.:
 *
 *	export LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so
 *	./v4lgrab >image.ppm
 *
 *	see http://hansdegoede.livejournal.com/3636.html for details.
 *
 */

#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 <linux/types.h>
#include <linux/videodev.h>

#define VIDEO_DEV "/dev/video0"

/* Stole this from tvset.c */

#define READ_VIDEO_PIXEL(buf, format, depth, r, g, b)                   \
{                                                                       \
	switch (format)                                                 \
	{                                                               \
		case VIDEO_PALETTE_GREY:                                \
			switch (depth)                                  \
			{                                               \
				case 4:                                 \
				case 6:                                 \
				case 8:                                 \
					(r) = (g) = (b) = (*buf++ << 8);\
					break;                          \
									\
				case 16:                                \
					(r) = (g) = (b) =               \
						*((unsigned short *) buf);      \
					buf += 2;                       \
					break;                          \
			}                                               \
			break;                                          \
									\
									\
		case VIDEO_PALETTE_RGB565:                              \
		{                                                       \
			unsigned short tmp = *(unsigned short *)buf;    \
			(r) = tmp&0xF800;                               \
			(g) = (tmp<<5)&0xFC00;                          \
			(b) = (tmp<<11)&0xF800;                         \
			buf += 2;                                       \
		}                                                       \
		break;                                                  \
									\
		case VIDEO_PALETTE_RGB555:                              \
			(r) = (buf[0]&0xF8)<<8;                         \
			(g) = ((buf[0] << 5 | buf[1] >> 3)&0xF8)<<8;    \
			(b) = ((buf[1] << 2 ) & 0xF8)<<8;               \
			buf += 2;                                       \
			break;                                          \
									\
		case VIDEO_PALETTE_RGB24:                               \
			(r) = buf[0] << 8; (g) = buf[1] << 8;           \
			(b) = buf[2] << 8;                              \
			buf += 3;                                       \
			break;                                          \
									\
		default:                                                \
			fprintf(stderr,                                 \
				"Format %d not yet supported\n",        \
				format);                                \
	}                                                               \
}

int get_brightness_adj(unsigned char *image, long size, int *brightness) {
  long i, tot = 0;
  for (i=0;i<size*3;i++)
    tot += image[i];
  *brightness = (128 - tot/(size*3))/3;
  return !((tot/(size*3)) >= 126 && (tot/(size*3)) <= 130);
}

int main(int argc, char ** argv)
{
  int fd = open(VIDEO_DEV, O_RDONLY), f;
  struct video_capability cap;
  struct video_window win;
  struct video_picture vpic;

  unsigned char *buffer, *src;
  int bpp = 24, r = 0, g = 0, b = 0;
  unsigned int i, src_depth = 16;

  if (fd < 0) {
    perror(VIDEO_DEV);
    exit(1);
  }

  if (ioctl(fd, VIDIOCGCAP, &cap) < 0) {
    perror("VIDIOGCAP");
    fprintf(stderr, "(" VIDEO_DEV " not a video4linux device?)\n");
    close(fd);
    exit(1);
  }

  if (ioctl(fd, VIDIOCGWIN, &win) < 0) {
    perror("VIDIOCGWIN");
    close(fd);
    exit(1);
  }

  if (ioctl(fd, VIDIOCGPICT, &vpic) < 0) {
    perror("VIDIOCGPICT");
    close(fd);
    exit(1);
  }

  if (cap.type & VID_TYPE_MONOCHROME) {
    vpic.depth=8;
    vpic.palette=VIDEO_PALETTE_GREY;    /* 8bit grey */
    if(ioctl(fd, VIDIOCSPICT, &vpic) < 0) {
      vpic.depth=6;
      if(ioctl(fd, VIDIOCSPICT, &vpic) < 0) {
	vpic.depth=4;
	if(ioctl(fd, VIDIOCSPICT, &vpic) < 0) {
	  fprintf(stderr, "Unable to find a supported capture format.\n");
	  close(fd);
	  exit(1);
	}
      }
    }
  } else {
    vpic.depth=24;
    vpic.palette=VIDEO_PALETTE_RGB24;

    if(ioctl(fd, VIDIOCSPICT, &vpic) < 0) {
      vpic.palette=VIDEO_PALETTE_RGB565;
      vpic.depth=16;

      if(ioctl(fd, VIDIOCSPICT, &vpic)==-1) {
	vpic.palette=VIDEO_PALETTE_RGB555;
	vpic.depth=15;

	if(ioctl(fd, VIDIOCSPICT, &vpic)==-1) {
	  fprintf(stderr, "Unable to find a supported capture format.\n");
	  return -1;
	}
      }
    }
  }

  buffer = malloc(win.width * win.height * bpp);
  if (!buffer) {
    fprintf(stderr, "Out of memory.\n");
    exit(1);
  }

  do {
    int newbright;
    read(fd, buffer, win.width * win.height * bpp);
    f = get_brightness_adj(buffer, win.width * win.height, &newbright);
    if (f) {
      vpic.brightness += (newbright << 8);
      if(ioctl(fd, VIDIOCSPICT, &vpic)==-1) {
	perror("VIDIOSPICT");
	break;
      }
    }
  } while (f);

  fprintf(stdout, "P6\n%d %d 255\n", win.width, win.height);

  src = buffer;

  for (i = 0; i < win.width * win.height; i++) {
    READ_VIDEO_PIXEL(src, vpic.palette, src_depth, r, g, b);
    fputc(r>>8, stdout);
    fputc(g>>8, stdout);
    fputc(b>>8, stdout);
  }

  close(fd);
  return 0;
}