请教：读取USB数码显微镜像素分辨率过小

hxf0223 · 发表于 2014-12-2 00:41:46

从淘宝上买了个无驱USB数码显微镜（应该跟摄像头一样的用法），连接到windows 7上，分辨率大概为640x480，截图分辨率达到1280x1024。
从网上找了些代码，调试运行后，发现几个问题不知如何解决：
1，设备的像素分辨率过低，只有160x120，为win7上的1/4，不知道该如何设置提高视频分辨率？
2，转换YUVY为BITMAP后，像素分辨率也只有160x120，不知该如何提高截图像素分辨率？

附1：初始化代码：

static int fd = -1;
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 enum_frame_intervals( int dev, __u32 pixfmt, __u32 width, __u32 height )
{
int ret;
struct v4l2_frmivalenum fival;
memset(&fival, 0, sizeof(fival));
fival.index = 0;
fival.pixel_format = pixfmt;
fival.width = width;
fival.height = height;
printf("\tTime interval between frame: ");
while ( (ret = ioctl(dev, VIDIOC_ENUM_FRAMEINTERVALS, &fival)) == 0 )
{
if (fival.type == V4L2_FRMIVAL_TYPE_DISCRETE) {
printf("%u/%u, ",
fival.discrete.numerator, fival.discrete.denominator);
} else if (fival.type == V4L2_FRMIVAL_TYPE_CONTINUOUS) {
printf("{min { %u/%u } .. max { %u/%u } }, ",
fival.stepwise.min.numerator, fival.stepwise.min.numerator,
fival.stepwise.max.denominator, fival.stepwise.max.denominator);
break;
} else if (fival.type == V4L2_FRMIVAL_TYPE_STEPWISE) {
printf("{min { %u/%u } .. max { %u/%u } / "
"stepsize { %u/%u } }, ",
fival.stepwise.min.numerator, fival.stepwise.min.denominator,
fival.stepwise.max.numerator, fival.stepwise.max.denominator,
fival.stepwise.step.numerator, fival.stepwise.step.denominator);
break;
}
fival.index++;
}
printf("\n");
if ( ret != 0 && errno != EINVAL ) {
perror("ERROR enumerating frame intervals");
return errno;
}
return 0;
}
static int enum_frame_sizes(int dev, __u32 pixfmt)
{
int ret;
struct v4l2_frmsizeenum fsize;
memset(&fsize, 0, sizeof(fsize));
fsize.index = 0;
fsize.pixel_format = pixfmt;
while ( (ret = ioctl(dev, VIDIOC_ENUM_FRAMESIZES, &fsize)) == 0 )
{
if (fsize.type == V4L2_FRMSIZE_TYPE_DISCRETE) {
printf("{ discrete: width = %u, height = %u }\n",
fsize.discrete.width, fsize.discrete.height);
ret = enum_frame_intervals(dev, pixfmt,
fsize.discrete.width, fsize.discrete.height);
if (ret != 0)
printf(" Unable to enumerate frame sizes.\n");
} else if (fsize.type == V4L2_FRMSIZE_TYPE_CONTINUOUS) {
printf("{ continuous: min { width = %u, height = %u } .. "
"max { width = %u, height = %u } }\n",
fsize.stepwise.min_width, fsize.stepwise.min_height,
fsize.stepwise.max_width, fsize.stepwise.max_height);
printf(" Refusing to enumerate frame intervals.\n");
break;
} else if (fsize.type == V4L2_FRMSIZE_TYPE_STEPWISE) {
printf("{ stepwise: min { width = %u, height = %u } .. "
"max { width = %u, height = %u } / "
"stepsize { width = %u, height = %u } }\n",
fsize.stepwise.min_width, fsize.stepwise.min_height,
fsize.stepwise.max_width, fsize.stepwise.max_height,
fsize.stepwise.step_width, fsize.stepwise.step_height);
printf(" Refusing to enumerate frame intervals.\n");
break;
}
fsize.index++;
}
if ( ret != 0 && errno != EINVAL ) {
perror("ERROR enumerating frame sizes");
return errno;
}
return 0;
}
static void video_list_formats( int dev )
{
struct v4l2_fmtdesc fmt;
int ret;
memset(&fmt, 0, sizeof(fmt));
fmt.index = 0;
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
while ( (ret = ioctl(dev, VIDIOC_ENUM_FMT, &fmt)) == 0 )
{
printf("{ pixelformat = '%c%c%c%c', description = '%s' }\n",
fmt.pixelformat & 0xFF, (fmt.pixelformat >> 8) & 0xFF,
(fmt.pixelformat >> 16) & 0xFF, (fmt.pixelformat >> 24) & 0xFF,
fmt.description);
ret = enum_frame_sizes(dev, fmt.pixelformat);
if ( ret != 0 )
printf("Unable to enumerate frame sizes.\n");
fmt.index++;
}
if ( errno != EINVAL ) {
perror("ERROR enumerating frame formats");
}
}
int init_v4l2(void)
{
//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
#if 0
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++;
}
#else
video_list_formats(fd);
#endif
//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;
}

复制代码

附2：采集及转换BITMAP代码：

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++ )
{
int wid = IMAGEWIDTH >> 1;
for ( j = 0; j < wid; j++ )
{
y1 = *(pointer + (i*wid+j)*4);
u = *(pointer + (i*wid+j)*4 + 1);
y2 = *(pointer + (i*wid+j)*4 + 2);
v = *(pointer + (i*wid+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 + ((IMAGEHEIGHT-1-i)*wid+j)*6) = (unsigned char)b1;
*(frame_buffer + ((IMAGEHEIGHT-1-i)*wid+j)*6 + 1) = (unsigned char)g1;
*(frame_buffer + ((IMAGEHEIGHT-1-i)*wid+j)*6 + 2) = (unsigned char)r1;
*(frame_buffer + ((IMAGEHEIGHT-1-i)*wid+j)*6 + 3) = (unsigned char)b2;
*(frame_buffer + ((IMAGEHEIGHT-1-i)*wid+j)*6 + 4) = (unsigned char)g2;
*(frame_buffer + ((IMAGEHEIGHT-1-i)*wid+j)*6 + 5) = (unsigned char)r2;
}
}
printf("change to RGB OK \n");
return 0;
}

复制代码

天嵌技术支持03 · 发表于 2014-12-2 11:01:13

fmt.fmt.pix.height = IMAGEHEIGHT;
fmt.fmt.pix.width = IMAGEWIDTH;
这里有没有正确设置

hxf0223 · 发表于 2014-12-2 12:27:05

天嵌技术支持03 发表于 2014-12-2 11:01
fmt.fmt.pix.height = IMAGEHEIGHT;
fmt.fmt.pix.width = IMAGEWIDTH;
这里有没有正确设 ...

谢谢大虾！

请教，这个是按照网上的帖子来的，如果不对该如何设置呢？

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请教：读取USB数码显微镜像素分辨率过小

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