# Revision history [back]

### OpenCV Noisy Disparity Map from Stereo Setup

I am trying to create a disparity map for depth calculations with my stereo camera setup. I have both cameras setup on tripods (relative same position with baseline of about 220mm). I have calibrated the cameras to obtain matrices for intrinsic and extrinsic parameters using OpenCV. When I try to create a disparity map I get a very noisy image that doesn't look right. I have played around with trying to normalize the images prior to using the StereoSGBM algorithm as you will see in my code. I have played around with the StereoSGBM parameters quite a bit and cant seem to get anything useful out of it. If you could offer any suggestions on how to fix this it would be much appreciated. I have attached my original images, rectified images, and my disparity map.

Images:

Here is a snippet from my code that shows my process and includes my parameters for my StereoSGBM.

cout << "Cam matrix 0: " << intParam[0].cameraMatrix.size() << endl;
cout << "Dist coeffs 0: " << intParam[0].distCoeffs.size() << endl;
cout << "Cam matrix 1: " << intParam[1].cameraMatrix.size() << endl;
cout << "Dist coeffs 1: " << intParam[1].distCoeffs.size() << endl;
cout << "Rotation matrix: " << extParam[0].rotation.size() << endl;
cout << "Translation matrix: " << extParam[0].translation.size() << endl;

Size imgSize (1440, 1080);
Mat RectMatrix0, RectMatrix1, projMatrix0, projMatrix1, Q;
// Q is a 4x4 disparity-depth mapping
Rect roi1, roi2;
// in stereo calib make struct Transformation {Rect and Proj}
stereoRectify(intParam[0].cameraMatrix, intParam[0].distCoeffs,
intParam[1].cameraMatrix, intParam[1].distCoeffs,
imgSize, extParam[0].rotation, extParam[0].translation,
RectMatrix0, RectMatrix1, projMatrix0, projMatrix1, Q,
CALIB_ZERO_DISPARITY, -1, imgSize, &roi1, &roi2);

Mat map11, map12, map21, map22;
initUndistortRectifyMap(intParam[0].cameraMatrix, intParam[0].distCoeffs,
RectMatrix0, projMatrix0, imgSize, CV_16SC2, map11, map12);
initUndistortRectifyMap(intParam[1].cameraMatrix, intParam[1].distCoeffs,
RectMatrix1, projMatrix1, imgSize, CV_16SC2, map21, map22);

Mat img1, img2; // Input Imgs
Mat img1r, img2r; // Rectified Imgs
Mat DispMap;

Mat img1_Resize, img2_Resize, img1r_Resize, img2r_Resize;

cvtColor(img1, img1, COLOR_BGR2GRAY);
cvtColor(img2, img2, COLOR_BGR2GRAY);
img1.convertTo(img1, CV_8U);
normalize(img1, img1, 0, 255, NORM_MINMAX);
img2.convertTo(img2, CV_8U);
normalize(img2, img2, 0, 255, NORM_MINMAX);

remap(img1, img1r, map11, map12, INTER_CUBIC);
remap(img2, img2r, map21, map22, INTER_CUBIC);

imwrite("cL0_rect.png", img1r);
imwrite("cR0_rect.png", img2r);
Mat img1_pnts, img2_pnts;

Size zero (0, 0);
resize(img1, img1_Resize, zero, 0.25, 0.25, INTER_LINEAR);
resize(img2, img2_Resize, zero, 0.25, 0.25, INTER_LINEAR);
resize(img1r, img1r_Resize, zero, 0.25, 0.25, INTER_LINEAR);
resize(img2r, img2r_Resize, zero, 0.25, 0.25, INTER_LINEAR);

imshow("Base 1", img1_Resize);
imshow("Base 2", img2_Resize);
imshow("Rectified 1", img1r_Resize);
imshow("Rectified 2", img2r_Resize);
waitKey();

int SADWindowSize = 3;
auto sgbm = StereoSGBM::create(   0,   //mindisp
16, //numdisp
P1,   //P1
P2,   //P2
144,   //dispdiffmax
63,   //prefiltercap
0,   //uniqueness
20,   //speckle window size
1,   //speckle range
cv::StereoSGBM::MODE_HH4);

sgbm->compute(img1r, img2r, DispMap);

Mat normDispMap, DispMap8u;
DispMap.convertTo(DispMap8u, CV_8U);
destroyAllWindows();
imshow("disparity", DispMap);
imshow("disparity 8u", DispMap8u);
waitKey();