常用的USB拍照功能代码： #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/videodev2.h> #include <malloc.h> #include <math.h> #include <string.h> #include <sys/mman.h> #include <errno.h> #include <assert.h> #include<QDebug> #include<QUuid> #include<QDir> #include<QDateTime> #include "uvcTest.h" #define FILE_VIDEO "/dev/video0" #define JPG "./p_w_picpath%d.jpg" BUFTYPE *usr_buf; static unsigned int n_buffer = 0; //set video capture ways(mmap) int init_mmap(int fd) { //to request frame cache, contain requested counts struct v4l2_requestbuffers reqbufs; //request V4L2 driver allocation video cache //this cache is locate in kernel and need mmap mapping memset(&reqbufs, 0, sizeof(reqbufs)); reqbufs.count = 4; reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; reqbufs.memory = V4L2_MEMORY_MMAP; if(-1 == ioctl(fd,VIDIOC_REQBUFS,&reqbufs)){ perror("Fail to ioctl 'VIDIOC_REQBUFS'"); exit(EXIT_FAILURE); } n_buffer = reqbufs.count; printf("n_buffer = %d\n", n_buffer); // usr_buf = (BUFTYPE *)calloc(reqbufs.count, sizeof(usr_buf)); usr_buf = new BUFTYPE[reqbufs.count*sizeof(BUFTYPE)]; if(usr_buf == NULL){ printf("Out of memory\n"); exit(-1); } //map kernel cache to user process for(n_buffer = 0; n_buffer < reqbufs.count; ++n_buffer){ //stand for a frame struct v4l2_buffer buf; memset(&buf, 0, sizeof(buf)); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = n_buffer; //check the information of the kernel cache requested if(-1 == ioctl(fd,VIDIOC_QUERYBUF,&buf)) { perror("Fail to ioctl : VIDIOC_QUERYBUF"); exit(EXIT_FAILURE); } usr_buf[n_buffer].length = buf.length; usr_buf[n_buffer].start = (char *)mmap( NULL, buf.length, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, buf.m.offset ); if(MAP_FAILED == usr_buf[n_buffer].start) { perror("Fail to mmap"); exit(EXIT_FAILURE); } } return 0; } //initial camera device int init_camera_device(int fd) { //decive fuction, such as video input struct v4l2_capability cap; //video standard,such as PAL,NTSC struct v4l2_standard std; //frame format struct v4l2_format tv_fmt; //check control struct v4l2_queryctrl query; //detail control value struct v4l2_fmtdesc fmt; int ret; //get the format of video supply memset(&fmt, 0, sizeof(fmt)); fmt.index = 0; //supply to p_w_picpath capture fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; // show all format of supply printf("Support format:\n"); while(ioctl(fd, VIDIOC_ENUM_FMT, &fmt) == 0){ fmt.index++; printf("pixelformat = ''%c%c%c%c''\ndescription = ''%s''\n",fmt.pixelformat & 0xFF, (fmt.pixelformat >> 8) & 0xFF,(fmt.pixelformat >> 16) & 0xFF, (fmt.pixelformat >> 24) & 0xFF,fmt.description); } //check video decive driver capability ret = ioctl(fd, VIDIOC_QUERYCAP, &cap); if(ret < 0){ perror("Fail to ioctl VIDEO_QUERYCAP"); exit(EXIT_FAILURE); } //judge wherher or not to be a video-get device if(!(cap.capabilities & V4L2_BUF_TYPE_VIDEO_CAPTURE)) { printf("The Current device is not a video capture device\n"); exit(-1); } //judge whether or not to supply the form of video stream if(!(cap.capabilities & V4L2_CAP_STREAMING)) { printf("The Current device does not support streaming i/o\n"); exit(EXIT_FAILURE); } //set the form of camera capture data tv_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; tv_fmt.fmt.pix.width = 100; tv_fmt.fmt.pix.height = 100; tv_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG; tv_fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; if (ioctl(fd, VIDIOC_S_FMT, &tv_fmt)< 0) { printf("VIDIOC_S_FMT\n"); exit(-1); close(fd); } //initial video capture way(mmap) init_mmap(fd); return 0; } int open_camera_device(const char *dev_name) { int fd; QString devName =QString(QLatin1String(dev_name)); QString strDevName = QString("sudo chmod 777 %1").arg(devName); qDebug()<<"strDevName"<<strDevName; // system(strDevName.toStdString().c_str()); //open video device with block fd = open(FILE_VIDEO, O_RDONLY); if(fd < 0){ perror(FILE_VIDEO); exit(EXIT_FAILURE); } return fd; } int start_capture(int fd) { unsigned int i; enum v4l2_buf_type type; //place the kernel cache to a queue for(i = 0; i < n_buffer; i++){ struct v4l2_buffer buf; memset(&buf, 0, sizeof(buf)); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = i; if(-1 == ioctl(fd, VIDIOC_QBUF, &buf)){ perror("Fail to ioctl 'VIDIOC_QBUF'"); exit(EXIT_FAILURE); } } //start capture data type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(-1 == ioctl(fd, VIDIOC_STREAMON, &type)){ printf("i=%d.\n", i); perror("VIDIOC_STREAMON"); close(fd); exit(EXIT_FAILURE); } return 0; } int process_p_w_picpath(void *addr, int length, int count, char *workOrder) { FILE *fp; count = 0; // static int num = 0; // char p_w_picpath_name[20]; char* p_w_picpath_name; QUuid id = QUuid::createUuid(); QString strId = id.toString(); strId.append(".jpeg"); // QString timeName = QDateTime::currentDateTime().toString("yyyyMMddhhmmss"); QString timeName = QString(QLatin1String(workOrder)); QDir dir("./photo"); if(!dir.exists()) dir.mkdir((dir.currentPath()+"/photo")); timeName.append(".jpeg"); // sprintf(p_w_picpath_name, JPG, count++); // strId.toLatin1(); QByteArray ba = timeName.toLatin1(); p_w_picpath_name=ba.data(); if((fp = fopen(p_w_picpath_name, "wb")) == NULL){ perror("Fail to fopen"); exit(EXIT_FAILURE); } fwrite(addr, length, 1, fp); usleep(500); fclose(fp); return 0; } int read_frame(int fd,char *workOrder) { struct v4l2_buffer buf; unsigned int i; memset(&buf, 0, sizeof(buf)); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; //put cache from queue if(-1 == ioctl(fd, VIDIOC_DQBUF,&buf)){ perror("Fail to ioctl 'VIDIOC_DQBUF'"); exit(EXIT_FAILURE); } assert(buf.index < n_buffer); //read process space's data to a file process_p_w_picpath(usr_buf[buf.index].start, usr_buf[buf.index].length,buf.index,workOrder); // qDebug()<<QString((char*)usr_buf[buf.index].start); if(-1 == ioctl(fd, VIDIOC_QBUF,&buf)){ perror("Fail to ioctl 'VIDIOC_QBUF'"); exit(EXIT_FAILURE); } return 1; } /** * @brief mainloop * @param fd 文件描述符 * @param count 拍摄的图片张数 * @return */ int mainloop(int fd, int count, char *workOrder) { // int count = 10; while(count-- > 0) { for(;;) { fd_set fds; struct timeval tv; int r; FD_ZERO(&fds); FD_SET(fd,&fds); /*Timeout*/ tv.tv_sec = 2; tv.tv_usec = 0; r = select(fd + 1,&fds,NULL,NULL,&tv); if(-1 == r) { if(EINTR == errno) continue; perror("Fail to select"); exit(EXIT_FAILURE); } if(0 == r) { fprintf(stderr,"select Timeout\n"); exit(-1); } if(read_frame(fd,workOrder)) break; } } return 0; } void stop_capture(int fd) { enum v4l2_buf_type type; type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(-1 == ioctl(fd,VIDIOC_STREAMOFF,&type)) { qDebug()<<"stop"<<fd; perror("Fail to ioctl 'VIDIOC_STREAMOFF'"); exit(EXIT_FAILURE); } return; } void close_camera_device(int fd) { unsigned int i; for(i = 0;i < n_buffer; i++) { if(-1 == munmap(usr_buf[i].start,usr_buf[i].length)){ exit(-1); } } delete[] usr_buf; // qDebug()<<"closedf"<<fd; if(-1 == close(fd)) { qDebug()<<"close"<<fd; perror("Fail to close fd"); exit(EXIT_FAILURE); } return; }免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
