复制代码- [/code]标记)
- 谢谢版主的解释，明白了不少，刚才又试了一个v4l2的例子；
- 把代码贴一下吧：
- [code]
- /* 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 <[email]philb@gnu.org[/email]>
- * Copied from [url]http://www.tazenda.demon.co.uk/phil/vgrabber.c[/url]
- * with minor modifications (Dave Forrest, [email]drf5n@virginia.edu[/email]).
- *
- *
- * For some cameras you may need to pre-load libv4l to perform
- * the necessary decompression, e.g.:
- *[color=#FF0000]
- * export LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so
- * ./v4lgrab >image.ppm
- *[/color] * see [url]http://hansdegoede.livejournal.com/3636.html[/url] 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, g, b;
- unsigned int i, src_depth;
- 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;
- }
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