单摄像头+激光测距
?如何用攝像頭來測距（opencv）
作者：郭世龍
???????最近一直忙著找工作，blog都長草了，今天把以前作的一個東西放上來充充門面吧。記得在哪看到過老外做的這個東西，覺得很好玩，就自己也做了一個。在攝像頭下面固定一個激光筆，就構成了這個簡易的測距裝置。看一下圖吧。
??原 理
??假設激光束是與攝像頭的光軸完全平行，激光束的中心落點在在攝像頭的視域中是最亮的點。激光束照射到攝像頭視域中的跟蹤目標上，那么攝像頭可以捕捉到這個點，通過簡單的圖像處理的方法，可以在這偵圖像中找到激光束照射形成的最亮點，同時可以計算出Y軸上方向上從落點到圖像中心的象素的個數。這個落點越接近圖像的中心，被測物體距離機器人就越遠。由下圖圖可以計算距離D：
（1）
??等式中h是一個常量，是攝像頭與激光發射器之間的垂直距離，可以直接測量獲得。
θ可通過下式計算： θ=Num*Rop+Offset??????（2）??????????????????????????? 其中：Num是從圖像中心到落點的像素個數 Rop是每個像素的弧度值 Offset是弧度誤差 合并以上等式可以得到： （3） Num可以從圖像上計算得到。Rop和Offset需要通過實驗計算獲得。首先測量出D的準確值，然后根據等式（1）可以計算出準確的θ，根據等式（2）可到只含有參數Rop和Offset的方程。在不同的距離多次測量D的準確值計算θ，求解方程組可以求出Rop和Offset。這里Rop＝0.0030354，Offset＝0.056514344。程 序 頭文件： class LaserRange?
{
public:
struct RangeResult * GetRange(IplImage * imgRange,IplImage * imgDst);
?LaserRange();
?virtual ~LaserRange();
? private:
????unsigned???int maxW;
???unsigned???int maxH;
????unsigned???int MaxPixel;
????RangeResult * strctResult;
???
?// Values used for calculating range from captured image data
?const double?gain;?// Gain Constant used for converting pixel offset to angle in radians
?const double?offset;?// Offset Constant
?const double?h_cm;??// Distance between center of camera and laser
????unsigned int?pixels_from_center;?// Brightest pixel location from center
?????? ?void Preprocess(void * img,IplImage * imgTemp);
}; cpp文件：
LaserRange::LaserRange():gain(0.0030354),offset(0),h_cm(4.542)
{
??maxW=0;
??maxH=0;
??MaxPixel=0;
??
??pixels_from_center=0;????// Brightest pixel location from center ??strctResult=new RangeResult;
?
??strctResult->maxCol=0;
??strctResult->maxRow=0;
??strctResult->maxPixel=0;
??strctResult->Range=0.0;
?} LaserRange::~LaserRange()
{
??if(NULL!=strctResult) delete strctResult;
} struct RangeResult * LaserRange::GetRange(IplImage * imgRange,IplImage * imgDst)
{?
????if(NULL==imgRange) return???strctResult;
???????Preprocess(imgRange,imgDst);
??????
????pixels_from_center = abs(120-maxH); ?// Calculate range in cm based on bright pixel location, and setup specific constants
?????strctResult->Range= h_cm/tan(pixels_from_center * gain + offset);
??????
????strctResult->PixfromCent=pixels_from_center;
???????strctResult->maxCol=maxW;
???????strctResult->maxRow=maxH;
???????strctResult->maxPixel=MaxPixel;
???????//strctResult->Range=0.0;
?????????return??strctResult;
}
void LaserRange::Preprocess(void *img, IplImage * imgTemp)
{
????MaxPixel=0;????????????????//處理下一幀前 最大像素值清零；
???IplImage* image = reinterpret_cast<IplImage*>(img);
???
???????cvCvtPixToPlane( image,0 ,0 ,imgTemp , 0);
??
??????for( int j=((imgTemp->width-60)/2-1); j<(imgTemp->width-40)/2+59; j++)?
??{
????for(int i=5; i<imgTemp->height-5; i++)
????{
???
????if((imgTemp->imageData[i*imgTemp->widthStep+j])>MaxPixel)
????{
?????if( ((imgTemp->imageData[(i-1)*imgTemp->widthStep+j])>MaxPixel) && ((imgTemp->imageData[(i-1)*imgTemp->widthStep+j+1])>MaxPixel) &&((imgTemp->imageData[(i-1)*imgTemp->widthStep+j-1])>MaxPixel)???)
?????{?
??????if( ((imgTemp->imageData[(i+1)*imgTemp->widthStep+j])>MaxPixel) && ((imgTemp->imageData[(i+1)*imgTemp->widthStep+j+1])>MaxPixel) &&((imgTemp->imageData[(i+1)*imgTemp->widthStep+j-1])>MaxPixel)???)
???????{
???????if((imgTemp->imageData[i*(imgTemp->widthStep)+j+1])>MaxPixel)
???????{
???????if((imgTemp->imageData[i*(imgTemp->widthStep)+j-1])>MaxPixel)
???????{
?????????MaxPixel=imgTemp->imageData[i*imgTemp->widthStep+j] ;
?????????maxW=j;
?????????maxH=i;
???????}
???????}
???????}
?????}
????}
??}
??????
} 調用函數： int CLaserVisionDlg::CaptureImage()
{
???// CvCapture* capture = 0;
?
???// capture = cvCaptureFromCAM(0);??//0表示設備號
????if( !capture )
????{
????????fprintf(stderr,"Could not initialize capturing.../n");
????????return -1;
????}
?
???// cvNamedWindow( "LaserRangeImage", 1 );
??// cvvNamedWindow( "image", 1);
???cvvNamedWindow( "Dimage", 1);
??
???for(;;)
????{
????????IplImage* frame = 0;
??????
??if(isStop) break; ????????frame = cvQueryFrame( capture );?//從攝像頭抓取一副圖像框架
????????if( !frame )
????????????break; ???????if( !imgOrign )
????????{
????????????//allocate all the buffers
????????????imgOrign = cvCreateImage( cvGetSize(frame), 8, 3 );????//創建一副圖像
????????????imgOrign->origin = frame->origin;
????
??} ????????cvCopy( frame, imgOrign, 0 );??//將圖frame復制到image
??//cvShowImage("LaserRangeImage",imgOrign);?
????
?
???????if(!imgDest)
????{
???imgDest=cvCreateImage( cvSize( imgOrign->width,imgOrign->height),8,1);
??????cvZero( imgDest );
????}
????????struct RangeResult * temp= laservsion.GetRange(imgOrign,imgDest);
??? ????????cvLine( imgOrign,cvPoint(temp->maxCol,0), cvPoint(temp->maxCol,imgOrign->height),cvScalar(100,100,255,0),1,8,0);
????????cvLine( imgOrign,cvPoint(0,temp->maxRow), cvPoint(imgOrign->width,temp->maxRow),cvScalar(100,100,255,0),1,8,0);
???
???????// cvvShowImage( "image", imgOrign);
??cvSaveImage("image.bmp", imgOrign);
?????????
????????cvvShowImage( "Dimage", imgDest);
??????
????????//在PictureBox上顯示圖片
??CDC* pDC = GetDlgItem(IDC_Picture)->GetDC();
????????CDC dcmemory;
????????BITMAP bm;
????????dcmemory.CreateCompatibleDC(pDC);
????????CBitmap* pBmp;
????????CString szFileName = "image.bmp";
????????HBITMAP hBk = (HBITMAP)::LoadImage(NULL,szFileName,IMAGE_BITMAP,0,0,LR_LOADFROMFILE);??
???????if(NULL!=hBk)??
????{
????????pBmp=CBitmap::FromHandle(hBk);
????????pBmp->GetObject(sizeof(BITMAP), &bm);
????????dcmemory.SelectObject(pBmp);
????????pDC->BitBlt(0, 0, bm.bmWidth, bm.bmHeight, &dcmemory, 0, 0, SRCCOPY); ????}
??????
??????
???????char str[80];?????????// To print message
????CDC *pDCp= GetDC();?
???????char str2[80];
?????
????// Display frame coordinates as well as calculated range
???????sprintf(str, "Pix Max Value=%d??At x= %u, y= %u, PixfromCent= %d",temp->maxPixel,temp->maxCol, temp->maxRow, temp->PixfromCent);
???????sprintf(str2, "Range= %f cm ",temp->Range);
???????pDCp->TextOut(30, 33, str);
???????pDCp->TextOut(50, 50, str2);
????ReleaseDC(pDCp);
????
??????int??c = cvWaitKey(10);
??????//??if( c == 'q' )
???????//?????break;
????? ?} //cvReleaseCapture( &capture );
//cvDestroyWindow("LaserRangeImage");
// cvDestroyWindow( "image");
?cvDestroyWindow( "Dimage");
return 0;
}
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